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On working steam expansively in marine engines
196
.Mechanics, Physics, and Chemis&y.
of gelatine is ]aid on a plane surface, such as glass, suffered to dry, and then plunged into a solution of a bi-chromate, whose base has no direct action on the gelatine; it is again dried, and then influenced eilher through a photogr~@fic negative or a positive picture, or in the focus of a camera. Afier the impression, which must vary with the intensity of the light, the layer is phmged into water; then all the parts which bare not received ~he influence of the light, swell and t'orm reliet~, while those which have been atI~cted absorb no water and remain as depressions. This surface is then transposed upon metal plates either by moulding in plaster o r b y the electrotype process. Tho second process which M. Portevin employs for the purpose of applying, photographically,.fatty matter upon pa.per, stone, or metallic surfaces by means of the actmn of light upon mixtures of chromates with gmnmy or mucilaginous matters, consists in applying one or more layers of this mixture upon the surfaces, and in impressing them, after drying, through the negatives of the pictures to be reproduced. Applying then, a fat ink by a tampon or roller~ it will adhere only on the parts which have been acted on by the light. He has also applied colors either in powder or otherwise upon various surfaces uoon the same principles. Several specimens were shown to the Academy.
On Working Sleam 2Exloa'nsivelyin .Ma~'ineE~gines. By Mr. E. ALLI~.* (Continued from page 138.)
Table V. gives the total space occupied by the machinery and coals relatively to the entire hulls, and includes the averages of six vessels with sidedever engines, and six vessels with direct-acting engines, all belonging to the Peninsular and Oriental Steam Navigation Company; also the a,eerage of 1200 English merchant vessels. From this Table it appears that from 34 to 44 per cent. of the whole capacily o~ the vessels is occupied by the engine-room and coals. The Table also~ gives the most general proportion of power to tonnage as one horse-power to every three tons. [The at~thor next gives in Tables VI. VII.,} the particulars of several steamers, with both screw and paddle-wheel engines, fi'om which the comparatb)e spaces occupied by the coals and machinery may be seen. From these Tables he deduces the following important particulars.] 1st. That in Government vessels the general proportion of coal taken is 1 ton pgr nominal horse-power, equal to about 1½ times the gross weight of lnachinery, as before given. ~*From tlie Lend. Mechanics' Magazine, Aug., 1855. 1" These aml several other Tables, which occur afterwards, we are compelled to omit, 'We arc, however, careful in all cases to give the results deduced from them, which will be suttieient tbr tile objects of the pal)er.~ED. M. M.
On Workin2 Steam Expansively in J'VIarineE~,gines.
t97
TM~L~ V.
i Average Average fl_verag; i R(glstered of Total . . . . . . Tonnage . . . Tonnage. Engine-romn. Tonnage. Avcragc of
Average [ Percentage of Avera e tota~-I ItorseEn,)'ine room to To g power. ITotalTonnage./Horse.power. t
to-
] n.ageperl
]
F
Side-lever Engines, P. and O. S. N. Co.
]
]
/
Average of 6 Direct-acting Englncs, P. and O. S. N. Co.
Averag~ of I200 Eng'lish Merchant Steamers. } - -
13S
10S
2,16
!
_ _
83
44 per cent.
2"95
2d. That tile horizontal space occupied by the entire englne-room, when this proportion of coal is taken, is about 4~ square feet per nominal horse-power. 3d. That the space oceupied by the coal hunkers carrying this proportion of' fuel, may be taken at 2 or 2¼ square feet per horse-power, or about three times the space occupied by the engines alone, exclusive of boilers, passages, &c. 4th. That the space occupied by the engines alone, exclusive of boilers, coal bunkers, and passages, may be taken at ¼ square feet per nominal horse-power, that is, where the engines are direct-acting. From an average of the eighteen estimates furnished to Government by difI~rent makers, and from some other cases, it appears that the space occupied by the boilers alone may be taken at about 1 square foot per nominal horse-power, and that the total price of £43 per horse-power for the machinery may be thus divided : ~ Engines, boilers, and coai bunkers, Wheels, Spare gear, Total,
88 0 0 per horse-power. 2 10 0 " " 2 10 0 " " £43
0
0
The amount for engines, &e., may be divided nearly as follows:-•£ s. 24 0 12 0 2 0
Engines, Boilers, Coal bunkers, Total,
£88
0
d. 0 per horse-power. 0 " " 0 " '-' 0
These proportions will be quite near enough for the purpose required, and the relation they hear to each other will not be much influenced by the present increased prices. It will therefore be assumed that the cost of the engines alone is about one-half the entire cost of machinery. It will be requisite further to consider the average annual expense of 17 *
i98
JVIe&anics, Physic6 and Chemistry.
the coal used by steam vessels, and its proportion to the cost of the yes. sels or capital ; this depending partly upon tile class of vessel, and partly upon the service upon whirl1 she is engaged. [In Table VIII., the author gives an approximation to the yearly cost of coal used by five classes of vessels, with the relation it bears to their
cost.]
These comparisons will be found useful when the advantages of increasing the size of the engines are considered. The cost of coal in London is taken at 16s. per ton. The cost of coal in Liverpool is taken at 1"2s. per ton. The cost of coal for Australian vessels at an average of 60s. per ton. The cost of coal tbr Eastern Steam Navigation Company at l'2s. per ton. The price of coal is sometimes above these amounts, but they are near enough to illustrate the argument intended, For better comparison, it will be desirable to condense the results, and this Table gives us the cost of engines alone (assumed at half the total cost of machinery) in " C l a s s e s 3,4, and 5, at 15 per cent. of the capital ; C l a s s 2~ at 20 per ~:ent. of the c a p i t a l ; C l a s s I, . at 30 per cer, t, of the c a p i t a l ;
Also the yearly cost of coal in Classes 2, 3, and 5, at say 5 per cent. of the capital ; Class 1, at say 15 per cent. of the capital ; .Class 4, at say 25 per cent. of the capital ;
In filrther illustration of this part of the' subject, the subjoined aceounls are added. [In Table IX. is given by the West India Mail Steam Packet Company an account, showi~,g the relative cost of coal, wages, &c., for 1850 and 1852, frum which it appears that the cost of coals in 1850, was equal to 30 per cent. r)f tile total working cost, and in 1852 equal to 35~ per cent.; and in Table X. is given the total actual expenses of coals, wages, &c., of the same Cm,q)any for the year 1850, and the per centages of these items ca the total cost of vessels.] 'ibis 'Fable gives the cost of coals in 1850 equal to 28 per cent. of tile working expenses, and nearly 13 per cent. of the tnlal cost of vessels, and the whole working expenses at 45~ per cent. of the cost of vessels. If the mileage working expenses for 1850 I)t. laken to amount to 45~ per cent. of the capital, then in 185"2 the same expenses would be 53}per cent., and from the respective ratios of the vost of coals to the total working expenses for those years, we have 13"74 per cent., anti 19'02 per cent. as the cost of coals on the capital; consequently 15 per cent. may be fairly taken as a mean. • T h e s e classes are a~ follows : - - l . River.
Italian.
2. Conllnc,ltal. g, Eastern Siesta l?avigation Com2oany.
3. American.
4, Aua.
On Working Steam Expansively in Jliarine Engines.
199
For easy reference the following Table XI. is given : ~ T.~I~LaXL When the ! Annual Cost of Coal on Capital i amounts respcctiwdy to i
5 per cent.
15 per cent.
25 per cent.
Then 10 per cent. saving in Coal ~ I .} p~r ecnt. on 1½ per cent. on 2,~ per cent. on eqmds ) i capital, capital, capital. " 20 " " " " !1 " 3 " 5 '. ,,
"
~o
40
.
"
.
.
.
"
.
.
"
.
.
"
t l~.
I2
,,
"
:q,
6
,,
"
,';:$
tO
,,
"
.As the least of these savings, in the middle column, fl'equenlly makes all the difference between a good and bad pa) ing concern, it is quite certain that upon the expenses of the single item of coal may frequently hang the very existence of a Compauy. It will be seen from lhe foregoing accounts, that there is little room for economizing the expenditure upon any other item, to anything like the extent possible in the item of coals alone, ~s the largest amount next that for coals, according to the mileage expenses, is for wages or repairs, eael', of these amounting to only about half the cost of the coals. The following Tables XII., XII[., XIV., have been compiled in order to show the increased dividend on original capital which ,nay be made by a sa~'ing in coal, owing to expansive working of the steam, the size or nominal horse-power of the eugiaes being supposed to be i,~ereased from I to 1,}, 2, 2}, and 3 times respectively, the extra cost of larger engines being proportionately allowed for, and the boilers attd wheels or screw supposed to remain tile same. The indicated or real horse-power is also supposed to remain the same, the larger engines being solely for the purpose of working the steam expansively. The first Table XII. is based on the supposition that the annual cost of coals is equal to 5 p e r cent.,on the eapitat, and nearly agrees with the classes of vessels numbered ~2, 3, and 5 in the Table VIII. This proportionate cost of coals is here applied to eases in which the cost of the engine power (exclusive of boilers, wheels, or screw), is equal to 15 per cent. of the capital, say as in Classes 3 and 5, and also to cases in which the cost of the engine power is 20 per cent. of the capital, as in Class "2. Column A, gives the proportionate size or nominal horse-power of engines ; ct~hnnn 13, the proportionate quantity of coal required to develop an equal amonnt of power (in each ease); column C, the proportionate cost of coal in pet' eentage of capital ; c o l u m n D, the proportionate saving in cost of coal in per eentage of capital, from which it appears that it" tim size of the engines he doubled, the saving is 1"45 per cent. on the capital, and if the size of the engines be increased to three times, the saving is 2'15 per cent. on the capital. F r o m this saving on the item of' coal, however, mast be deducted the interest on the extra cost of larger engines, and this deduction will vary according to the proportionate expenses of the engines to the capital. Columns E, F, G, apply to the ease in which the cost of the engines alone (exclusive of boilers, wheels, or scre~ ~) amounts to I 5 per cent. of capital (as
~00
~Iechanics, Physics, antl Chemistry.
in American vessels, and the Eastern Steam Navigation Company); and columns tI, I, J, to the ease in which lhe eost of engines alone amounts to 20 per cent. of capital, as in eontinemal sieamc'rs, &~:.; columns E and H give the necessary per ceatage of' increase of capiial; columns F and I the permanent cliarge on capital, being 5 per cent. allowed on the necessary addition made to it ; and eohimns G and J, the gross gain in per centage of eal:m< 1, after dedncting tim in~erest on extra cost of engines f."om the total gain or sating in coal. The results in this Table .show that if the size of the engi~es be doubled, an additional 0'70 or 0"45 per cent. may be paid on capila], and that upon the engines being increased to three times the size, an additional 0"(~5 or 0"15 per cent. may be paid on capital, aecordii~g as the cost of tile engine power amounts to 15 per cent. or 20 per eent. of the capital respectively. TxBI~V', X r I . Table sDowlng lhe Increa,s.ed Dividend on Capilui,. b?< a Saving in, (;7>alfrom E;~TJan-
si're ltTn']~'inlf; lhe ca:h'a Co,~'t qf larg'cr ]O~gine,~ beD~g tal,'en i~Uo accounl; Boilers, Wheels, or Screwy, and lndiraled Jf(n'se-l'ower being supposed lo ~'emain lhe ,same. I
I
[
t
llorsoPower,
or s i z e of Engines.
1
~ 2 ~ 21/-
,
ANNUAL COSI: OF eO~l.S 'r.tK~:N AT I:IVE I~EI1. CKNT. OF CAPITAL.
, I Ca~t oi' Enf~im~s M o n e O,xehl~gaving in[ s i r e of Boilm.s, ~l:rew, &e.:j Cost o f ~ (:~lua! (sayto 15 per cent. o;3f &CapiL coal ill i cost of" i 5). coal ill | _ _ ~ . as i. n Olnsses . . per eel/t-, i coal for per cent-|.. i Gross~ ] same . . . . l ~e toPillell~ " eli °riv~in tl ] . . 11 l "~t!,(, NOllti~.'1111 [ acttial eal)[tal. {'~ a 11 - | m d h o r s e - e h : t r g e oil (!'ll)i{'d, I Power. a u e t i•l l g ' ira. power, C a p"i t a l , t e"< ndds to being 5 amounts I C:tpigM ; per el'ill;. iu ~' f r o m I inve~-ted, on~uldiVn D,
1.o) .sl -71 63 II
P ( r Ct' i t P e r ConB.IPc r Co)It 5.oo . i • • <~.t),~ i .,l~ I T.,~o 3"55 i 1.45 i 15,o 3'15 I 1~5 I 22"50
c,
"
I
E
i
C os t o f E u g i n e s a l o n e ( e x c l u s i v e of i B oile rs , S c r e w , & c . ) e q u a ] to 2 ° peri (s a y as i n C l a s s 2). 1i e~nlt, o f " [ Ii el'etlSill,~ . . . . . . . . .~. . .1. . .POl'lll/t. . . . . . . . . . . . . . [(~1 . . " t h e Nolni-i ...... ~ 51°osl~ i~{~ n a ] or~e c h ' l r , , e m l . '~ p :' * ~ta : ( I{}(1u c t lnl~ 1]ow r ~ ca] ." : . : :HtlO ~1 l[S {trill8 to ll)Olllp' 5 p e r i n I tk'olJJ. eapiLal in-; ccmL o n i D. vested, i addi[ion, i
:Per C e n t Per Co n L i . . . . ! '.~T i '75 "71 1"12 '7 o
I P er C e n t . P e r Cent. i . . . . ! 70'oo I ':'o I ~,o'00 I I'00 I 5 "0o [ 1,5)
! I I [
Per CcnL • .,i5 "45 'J5
i
i
,
J
.;i:
~'
I
cl
I~
,
:
The second Table, XlII., is constructed in the saille Inantler as the first, the annual cost of coals being taken at 15 per cent. of the capital, which, as before mentioned, applies to the class of vesseIs marked 1, and the West India Mail boats. This minual cost of coals is applied to the cases in which the cost of engines (exclusive of boilers, wheels, or screw), amounts to 20 per cent. of the capital, and also to the cases in which the cost of engines alone araounts to 30 per cent. of the capital; the general results are, that if the engines be inereased to dqnble the size, tot the sake of expansive working, the saving of" coal Would be 4'35 per cent. of capital, and if the engines be increased to three times the size, the saving in coal ~vould be 6"45 per cent. of capital. These amounts are reduced by the extra cost of engines respectively to 3"55 per cent. and 2"85 per cent. of capital, and to 4'45 per Cent. and 3.45 per cent. of capital, according as the cost of engine pow!r amounts to 20 per cent. or 30 per cent. of capital. The third Table, XIV., is constructed in the same man~er as the two former ones, the annual cost of coals being taken at 25 pdt cent. of the
On Working Steam Expansively in 311arineEngines.
201"
capital, which, as shown bet'ore, applies to the Australian vessels, or class 4, where the cost of engines alone (exclusive of boilers, wheels, or screw), is equal to about 15 per cent. of capital. The results are, that if the size of the engines be doubled for expansive working, the saving of coal would amount to 7"25 per cent. of capital, and if increased to three times the size, the saving of coal would amount to 10"'/5 per cent. of capital. These amounts are reduced by the extra cost of engines to 6'50 per cent. and 9.'25 per cent. of capital. TAw,~ XIII.
Table showing the Increased Dividend by a Savlng'in Coal from Expansive Working, the extra Cost of iarg,cr Engines being taken into account ; Boilers, Wheels, or Screw, and Indicated IIorse-Power being supposed to remain the same. A N N U A L COST OF COALS T A K E N AT FIFTEEN P E R CENT, OF CAPITAL.
I
P~op?r-~'~.opo r-
Cost o [ coal in iPer con [ age of I origina i capital
ICost of Engines alone (( xclusive iof Boilers, Screw, &c. equals Saving inl20 per cent. of capita] (as in cost of [West India Mail Boats.) coal in ~Increasing -1'erm~{---~3er cent- [the N0min e n t ]G ross gain ' age of |naI horsc~ charge on o t capital. original ] power capital, Id :ducting" capital. ] a d d s to beingSper] ~mounts [capital in- cent. on ill F from
--I-
l--~r
~r ] P~r
,.oo[C nt.
1
3"
Pe~
fco t.
•81
1 .oo 12"15
.71
i0.65
63 ••57
9"45 8"55
;51 35! ~5~ ~:5 ~
lo :o so 40
I :P~r
Boats, Class 13
[ PermaGross Increasing [ nent gain on Nominal charge on cap tal, ]orse-powcr, I capital~ deduct'g I ldds to capi- being5 pc: amounts I ial invested.] cont. ou i n l f r o m J addition____~ D.
Con . I Ce, t.
Cent.
I 'g I 1.oo I 3,35 II 2"00 1.50 I 4.05
,0 45
4"45
c
A
2os~ of Engines alone (exclusiv e )f Boilers, Screw, &e.) equals 20 ~er cent. of capital, (a~ in River
Cent.
.
[vso /~'25
12"85 /z'z°
60 [~.oo 13.45 ----:a--C-T-V-T-
TABL~ X I V .
Table'showlng" the Increased Dividend by a Saving in Coal from Expansive Working, the extra Cost of Larger Engines being taken into account ; Boilers, Wheels, or Screw, and Indicated Horse-Power being supposed to remain the same. A N N U A L COST OF COALS T A K E N AT c25 P E R CE~T, OF CAPITAL,
Propor- ~ Propor- ]. . . . . . . . . I ' - - - ~ C o s t of En.'ines alone'-(cxclusive of Boilers, .... tional ] cost tional Screw. &c.~ equal to 15 per cent of eapital, ]} nominal of "Cost of coal Saving in | (as in Australian Vcssels~ Class 4.) / nersccoal for t in per cent* cost of coal | . . . . . . . . . . . . . . . . . / Power, or same age oforigi- in per cent- | l)ermancnt Gross gum on ] size of actu/d nM capital. age of origi- | Increasing the n~l capital. | Nominal IIorse- charge on capital, capital, deduct~ngines. power. | power, adds to being 5 per cert. ing tile a m o u n ~ |capital invested, on addition, in F from D: 1
1'00
1~
"81
2 t ~½
.71 .63
3
"57
1
Per Cent.
Ipe,.'d 'nt.
:5o0
20"25 17"75 15"75
] [
i.go
7'25 9'25
,4.5 fp C
Ce, C ent.
4;i
t 1)
_
P e r Cent.
:J7
15.00 22.50 30.00
•75 1"12 1"50
E
F
Per Cent.
i. s 6.50 8.13 9.25
_
G
202
&leehanics, Physics, and Chemistry.
It is evident that the dearer the coal is, or the larger the quantity consumed in proportion to the actual power developed, the more advantageous would be the saving effected by expansive working, as the per centage of saving in coal would the sooner cover any extra cost of" engin;: ;b:nidn:lr;:O~eg:i~gr2f~:::s cfloe)r~Ys):Wv2h~,~frk~hne si::dOfthtehi; engin " , " ' p " " g, "r cost be consequently doubled, there yet remains a gain, under the worst circumstances, of "15 per cent. Oll capital, and under favorable eircum. stances, such as those presented by the Australian vessels, of 9~ per cent. on capital.* be continued.)
(To
TWENTY-FIFTH
MEETING
OF THE
ADVANCEMENT
BRITISH ASSOCIATION OF
:FOR T H I I
SCIENCE. t
On t}~e Condition of the .3tmosphere during Cholera. By Dr. R. D. T~1oMsoN.--The chemical condition of cholera atmospheres is a question of intense interest in the subject of public health ; but, with the exception of the unpublished experiments of Dr. Prout, in 183"2, comparatively little attention appears to have been bestowed on it. One of the most striking circumstances connected with the occurrence of the disease is, that no change very palpable to the senses prevails, and even one may have remarked that the weather has usually been exceedingly agreeable. In London, at St. Thomas's Hospital, the neighborhood of which afforded a large supply of cholera eases, the relative weight of the air in August, 1854, a cholera month, and in August, 1855, when the metropolis was in an extremely healthy condition, is exhibited in the following table, in grains per cubic foot : - 1854. Weight Week ending August 5 .. " 12 ", " 19 .. " 26 .. Sept. 2 .. " 9 .. Mean
..
of Cubic iF. in grains. 522'9 g r a i n s 526'7 " 595,0 " 523'5 " 525.1 " 530'3 " 525.6
"
1855. W e i g h t of Cublc F t . Week ending in grains. August 4 .. 516.9 g r a i n s " 11 ". 524.3 ,, " 18 .. 525'9 " ,c 25 .. 519.2 '¢ Sept. l .. 523'0 " " 8 ., 531.6 " Mean
..
523"5
"
The result, as deduced from tills table, which has been calculated approximately from the barometric pressure and dry and wet bulb thermometer, is analogous to that obtained by Dr. Prout, in 1832, as the author was informed by himself. Corresponding observations have been made at Greenwich by Mr. Glaisher, and the same conclusions arrived at ; from which it would appear that this superior weight of a given bulk I t has not been considered necessary to i n c l u d e more t h a n the tlve classes of vess e l s i n the tbregoing Tables, although m a n y o t h e r classes exist, in w h i c h the propert i o n a t e cost of coal and m a c h i n e r y vary from the a m o u n t s given. In order, however, t o a s c e r t a i n what a d v a n t a g e s would be gained b y the substitution of larger e n g i n e s in a n y specific case, it will only be neeessalT to substitute the correct a m o u n t s i n place of t h o s e g i v e n above. 1" :From the Lond. A t h c n m u m , September, 1855.
.Mechanics, Physics, and Chemis&y.
of gelatine is ]aid on a plane surface, such as glass, suffered to dry, and then plunged into a solution of a bi-chromate, whose base has no direct action on the gelatine; it is again dried, and then influenced eilher through a photogr~@fic negative or a positive picture, or in the focus of a camera. Afier the impression, which must vary with the intensity of the light, the layer is phmged into water; then all the parts which bare not received ~he influence of the light, swell and t'orm reliet~, while those which have been atI~cted absorb no water and remain as depressions. This surface is then transposed upon metal plates either by moulding in plaster o r b y the electrotype process. Tho second process which M. Portevin employs for the purpose of applying, photographically,.fatty matter upon pa.per, stone, or metallic surfaces by means of the actmn of light upon mixtures of chromates with gmnmy or mucilaginous matters, consists in applying one or more layers of this mixture upon the surfaces, and in impressing them, after drying, through the negatives of the pictures to be reproduced. Applying then, a fat ink by a tampon or roller~ it will adhere only on the parts which have been acted on by the light. He has also applied colors either in powder or otherwise upon various surfaces uoon the same principles. Several specimens were shown to the Academy.
On Working Sleam 2Exloa'nsivelyin .Ma~'ineE~gines. By Mr. E. ALLI~.* (Continued from page 138.)
Table V. gives the total space occupied by the machinery and coals relatively to the entire hulls, and includes the averages of six vessels with sidedever engines, and six vessels with direct-acting engines, all belonging to the Peninsular and Oriental Steam Navigation Company; also the a,eerage of 1200 English merchant vessels. From this Table it appears that from 34 to 44 per cent. of the whole capacily o~ the vessels is occupied by the engine-room and coals. The Table also~ gives the most general proportion of power to tonnage as one horse-power to every three tons. [The at~thor next gives in Tables VI. VII.,} the particulars of several steamers, with both screw and paddle-wheel engines, fi'om which the comparatb)e spaces occupied by the coals and machinery may be seen. From these Tables he deduces the following important particulars.] 1st. That in Government vessels the general proportion of coal taken is 1 ton pgr nominal horse-power, equal to about 1½ times the gross weight of lnachinery, as before given. ~*From tlie Lend. Mechanics' Magazine, Aug., 1855. 1" These aml several other Tables, which occur afterwards, we are compelled to omit, 'We arc, however, careful in all cases to give the results deduced from them, which will be suttieient tbr tile objects of the pal)er.~ED. M. M.
On Workin2 Steam Expansively in J'VIarineE~,gines.
t97
TM~L~ V.
i Average Average fl_verag; i R(glstered of Total . . . . . . Tonnage . . . Tonnage. Engine-romn. Tonnage. Avcragc of
Average [ Percentage of Avera e tota~-I ItorseEn,)'ine room to To g power. ITotalTonnage./Horse.power. t
to-
] n.ageperl
]
F
Side-lever Engines, P. and O. S. N. Co.
]
]
/
Average of 6 Direct-acting Englncs, P. and O. S. N. Co.
Averag~ of I200 Eng'lish Merchant Steamers. } - -
13S
10S
2,16
!
_ _
83
44 per cent.
2"95
2d. That tile horizontal space occupied by the entire englne-room, when this proportion of coal is taken, is about 4~ square feet per nominal horse-power. 3d. That the space oceupied by the coal hunkers carrying this proportion of' fuel, may be taken at 2 or 2¼ square feet per horse-power, or about three times the space occupied by the engines alone, exclusive of boilers, passages, &c. 4th. That the space occupied by the engines alone, exclusive of boilers, coal bunkers, and passages, may be taken at ¼ square feet per nominal horse-power, that is, where the engines are direct-acting. From an average of the eighteen estimates furnished to Government by difI~rent makers, and from some other cases, it appears that the space occupied by the boilers alone may be taken at about 1 square foot per nominal horse-power, and that the total price of £43 per horse-power for the machinery may be thus divided : ~ Engines, boilers, and coai bunkers, Wheels, Spare gear, Total,
88 0 0 per horse-power. 2 10 0 " " 2 10 0 " " £43
0
0
The amount for engines, &e., may be divided nearly as follows:-•£ s. 24 0 12 0 2 0
Engines, Boilers, Coal bunkers, Total,
£88
0
d. 0 per horse-power. 0 " " 0 " '-' 0
These proportions will be quite near enough for the purpose required, and the relation they hear to each other will not be much influenced by the present increased prices. It will therefore be assumed that the cost of the engines alone is about one-half the entire cost of machinery. It will be requisite further to consider the average annual expense of 17 *
i98
JVIe&anics, Physic6 and Chemistry.
the coal used by steam vessels, and its proportion to the cost of the yes. sels or capital ; this depending partly upon tile class of vessel, and partly upon the service upon whirl1 she is engaged. [In Table VIII., the author gives an approximation to the yearly cost of coal used by five classes of vessels, with the relation it bears to their
cost.]
These comparisons will be found useful when the advantages of increasing the size of the engines are considered. The cost of coal in London is taken at 16s. per ton. The cost of coal in Liverpool is taken at 1"2s. per ton. The cost of coal for Australian vessels at an average of 60s. per ton. The cost of coal tbr Eastern Steam Navigation Company at l'2s. per ton. The price of coal is sometimes above these amounts, but they are near enough to illustrate the argument intended, For better comparison, it will be desirable to condense the results, and this Table gives us the cost of engines alone (assumed at half the total cost of machinery) in " C l a s s e s 3,4, and 5, at 15 per cent. of the capital ; C l a s s 2~ at 20 per ~:ent. of the c a p i t a l ; C l a s s I, . at 30 per cer, t, of the c a p i t a l ;
Also the yearly cost of coal in Classes 2, 3, and 5, at say 5 per cent. of the capital ; Class 1, at say 15 per cent. of the capital ; .Class 4, at say 25 per cent. of the capital ;
In filrther illustration of this part of the' subject, the subjoined aceounls are added. [In Table IX. is given by the West India Mail Steam Packet Company an account, showi~,g the relative cost of coal, wages, &c., for 1850 and 1852, frum which it appears that the cost of coals in 1850, was equal to 30 per cent. r)f tile total working cost, and in 1852 equal to 35~ per cent.; and in Table X. is given the total actual expenses of coals, wages, &c., of the same Cm,q)any for the year 1850, and the per centages of these items ca the total cost of vessels.] 'ibis 'Fable gives the cost of coals in 1850 equal to 28 per cent. of tile working expenses, and nearly 13 per cent. of the tnlal cost of vessels, and the whole working expenses at 45~ per cent. of the cost of vessels. If the mileage working expenses for 1850 I)t. laken to amount to 45~ per cent. of the capital, then in 185"2 the same expenses would be 53}per cent., and from the respective ratios of the vost of coals to the total working expenses for those years, we have 13"74 per cent., anti 19'02 per cent. as the cost of coals on the capital; consequently 15 per cent. may be fairly taken as a mean. • T h e s e classes are a~ follows : - - l . River.
Italian.
2. Conllnc,ltal. g, Eastern Siesta l?avigation Com2oany.
3. American.
4, Aua.
On Working Steam Expansively in Jliarine Engines.
199
For easy reference the following Table XI. is given : ~ T.~I~LaXL When the ! Annual Cost of Coal on Capital i amounts respcctiwdy to i
5 per cent.
15 per cent.
25 per cent.
Then 10 per cent. saving in Coal ~ I .} p~r ecnt. on 1½ per cent. on 2,~ per cent. on eqmds ) i capital, capital, capital. " 20 " " " " !1 " 3 " 5 '. ,,
"
~o
40
.
"
.
.
.
"
.
.
"
.
.
"
t l~.
I2
,,
"
:q,
6
,,
"
,';:$
tO
,,
"
.As the least of these savings, in the middle column, fl'equenlly makes all the difference between a good and bad pa) ing concern, it is quite certain that upon the expenses of the single item of coal may frequently hang the very existence of a Compauy. It will be seen from lhe foregoing accounts, that there is little room for economizing the expenditure upon any other item, to anything like the extent possible in the item of coals alone, ~s the largest amount next that for coals, according to the mileage expenses, is for wages or repairs, eael', of these amounting to only about half the cost of the coals. The following Tables XII., XII[., XIV., have been compiled in order to show the increased dividend on original capital which ,nay be made by a sa~'ing in coal, owing to expansive working of the steam, the size or nominal horse-power of the eugiaes being supposed to be i,~ereased from I to 1,}, 2, 2}, and 3 times respectively, the extra cost of larger engines being proportionately allowed for, and the boilers attd wheels or screw supposed to remain tile same. The indicated or real horse-power is also supposed to remain the same, the larger engines being solely for the purpose of working the steam expansively. The first Table XII. is based on the supposition that the annual cost of coals is equal to 5 p e r cent.,on the eapitat, and nearly agrees with the classes of vessels numbered ~2, 3, and 5 in the Table VIII. This proportionate cost of coals is here applied to eases in which the cost of the engine power (exclusive of boilers, wheels, or screw), is equal to 15 per cent. of the capital, say as in Classes 3 and 5, and also to cases in which the cost of the engine power is 20 per cent. of the capital, as in Class "2. Column A, gives the proportionate size or nominal horse-power of engines ; ct~hnnn 13, the proportionate quantity of coal required to develop an equal amonnt of power (in each ease); column C, the proportionate cost of coal in pet' eentage of capital ; c o l u m n D, the proportionate saving in cost of coal in per eentage of capital, from which it appears that it" tim size of the engines he doubled, the saving is 1"45 per cent. on the capital, and if the size of the engines be increased to three times, the saving is 2'15 per cent. on the capital. F r o m this saving on the item of' coal, however, mast be deducted the interest on the extra cost of larger engines, and this deduction will vary according to the proportionate expenses of the engines to the capital. Columns E, F, G, apply to the ease in which the cost of the engines alone (exclusive of boilers, wheels, or scre~ ~) amounts to I 5 per cent. of capital (as
~00
~Iechanics, Physics, antl Chemistry.
in American vessels, and the Eastern Steam Navigation Company); and columns tI, I, J, to the ease in which lhe eost of engines alone amounts to 20 per cent. of capital, as in eontinemal sieamc'rs, &~:.; columns E and H give the necessary per ceatage of' increase of capiial; columns F and I the permanent cliarge on capital, being 5 per cent. allowed on the necessary addition made to it ; and eohimns G and J, the gross gain in per centage of eal:m< 1, after dedncting tim in~erest on extra cost of engines f."om the total gain or sating in coal. The results in this Table .show that if the size of the engi~es be doubled, an additional 0'70 or 0"45 per cent. may be paid on capila], and that upon the engines being increased to three times the size, an additional 0"(~5 or 0"15 per cent. may be paid on capital, aecordii~g as the cost of tile engine power amounts to 15 per cent. or 20 per eent. of the capital respectively. TxBI~V', X r I . Table sDowlng lhe Increa,s.ed Dividend on Capilui,. b?< a Saving in, (;7>alfrom E;~TJan-
si're ltTn']~'inlf; lhe ca:h'a Co,~'t qf larg'cr ]O~gine,~ beD~g tal,'en i~Uo accounl; Boilers, Wheels, or Screwy, and lndiraled Jf(n'se-l'ower being supposed lo ~'emain lhe ,same. I
I
[
t
llorsoPower,
or s i z e of Engines.
1
~ 2 ~ 21/-
,
ANNUAL COSI: OF eO~l.S 'r.tK~:N AT I:IVE I~EI1. CKNT. OF CAPITAL.
, I Ca~t oi' Enf~im~s M o n e O,xehl~gaving in[ s i r e of Boilm.s, ~l:rew, &e.:j Cost o f ~ (:~lua! (sayto 15 per cent. o;3f &CapiL coal ill i cost of" i 5). coal ill | _ _ ~ . as i. n Olnsses . . per eel/t-, i coal for per cent-|.. i Gross~ ] same . . . . l ~e toPillell~ " eli °riv~in tl ] . . 11 l "~t!,(, NOllti~.'1111 [ acttial eal)[tal. {'~ a 11 - | m d h o r s e - e h : t r g e oil (!'ll)i{'d, I Power. a u e t i•l l g ' ira. power, C a p"i t a l , t e"< ndds to being 5 amounts I C:tpigM ; per el'ill;. iu ~' f r o m I inve~-ted, on~uldiVn D,
1.o) .sl -71 63 II
P ( r Ct' i t P e r ConB.IPc r Co)It 5.oo . i • • <~.t),~ i .,l~ I T.,~o 3"55 i 1.45 i 15,o 3'15 I 1~5 I 22"50
c,
"
I
E
i
C os t o f E u g i n e s a l o n e ( e x c l u s i v e of i B oile rs , S c r e w , & c . ) e q u a ] to 2 ° peri (s a y as i n C l a s s 2). 1i e~nlt, o f " [ Ii el'etlSill,~ . . . . . . . . .~. . .1. . .POl'lll/t. . . . . . . . . . . . . . [(~1 . . " t h e Nolni-i ...... ~ 51°osl~ i~{~ n a ] or~e c h ' l r , , e m l . '~ p :' * ~ta : ( I{}(1u c t lnl~ 1]ow r ~ ca] ." : . : :HtlO ~1 l[S {trill8 to ll)Olllp' 5 p e r i n I tk'olJJ. eapiLal in-; ccmL o n i D. vested, i addi[ion, i
:Per C e n t Per Co n L i . . . . ! '.~T i '75 "71 1"12 '7 o
I P er C e n t . P e r Cent. i . . . . ! 70'oo I ':'o I ~,o'00 I I'00 I 5 "0o [ 1,5)
! I I [
Per CcnL • .,i5 "45 'J5
i
i
,
J
.;i:
~'
I
cl
I~
,
:
The second Table, XlII., is constructed in the saille Inantler as the first, the annual cost of coals being taken at 15 per cent. of the capital, which, as before mentioned, applies to the class of vesseIs marked 1, and the West India Mail boats. This minual cost of coals is applied to the cases in which the cost of engines (exclusive of boilers, wheels, or screw), amounts to 20 per cent. of the capital, and also to the cases in which the cost of engines alone araounts to 30 per cent. of the capital; the general results are, that if the engines be inereased to dqnble the size, tot the sake of expansive working, the saving of" coal Would be 4'35 per cent. of capital, and if the engines be increased to three times the size, the saving in coal ~vould be 6"45 per cent. of capital. These amounts are reduced by the extra cost of engines respectively to 3"55 per cent. and 2"85 per cent. of capital, and to 4'45 per Cent. and 3.45 per cent. of capital, according as the cost of engine pow!r amounts to 20 per cent. or 30 per cent. of capital. The third Table, XIV., is constructed in the same man~er as the two former ones, the annual cost of coals being taken at 25 pdt cent. of the
On Working Steam Expansively in 311arineEngines.
201"
capital, which, as shown bet'ore, applies to the Australian vessels, or class 4, where the cost of engines alone (exclusive of boilers, wheels, or screw), is equal to about 15 per cent. of capital. The results are, that if the size of the engines be doubled for expansive working, the saving of coal would amount to 7"25 per cent. of capital, and if increased to three times the size, the saving of coal would amount to 10"'/5 per cent. of capital. These amounts are reduced by the extra cost of engines to 6'50 per cent. and 9.'25 per cent. of capital. TAw,~ XIII.
Table showing the Increased Dividend by a Savlng'in Coal from Expansive Working, the extra Cost of iarg,cr Engines being taken into account ; Boilers, Wheels, or Screw, and Indicated IIorse-Power being supposed to remain the same. A N N U A L COST OF COALS T A K E N AT FIFTEEN P E R CENT, OF CAPITAL.
I
P~op?r-~'~.opo r-
Cost o [ coal in iPer con [ age of I origina i capital
ICost of Engines alone (( xclusive iof Boilers, Screw, &c. equals Saving inl20 per cent. of capita] (as in cost of [West India Mail Boats.) coal in ~Increasing -1'erm~{---~3er cent- [the N0min e n t ]G ross gain ' age of |naI horsc~ charge on o t capital. original ] power capital, Id :ducting" capital. ] a d d s to beingSper] ~mounts [capital in- cent. on ill F from
--I-
l--~r
~r ] P~r
,.oo[C nt.
1
3"
Pe~
fco t.
•81
1 .oo 12"15
.71
i0.65
63 ••57
9"45 8"55
;51 35! ~5~ ~:5 ~
lo :o so 40
I :P~r
Boats, Class 13
[ PermaGross Increasing [ nent gain on Nominal charge on cap tal, ]orse-powcr, I capital~ deduct'g I ldds to capi- being5 pc: amounts I ial invested.] cont. ou i n l f r o m J addition____~ D.
Con . I Ce, t.
Cent.
I 'g I 1.oo I 3,35 II 2"00 1.50 I 4.05
,0 45
4"45
c
A
2os~ of Engines alone (exclusiv e )f Boilers, Screw, &e.) equals 20 ~er cent. of capital, (a~ in River
Cent.
.
[vso /~'25
12"85 /z'z°
60 [~.oo 13.45 ----:a--C-T-V-T-
TABL~ X I V .
Table'showlng" the Increased Dividend by a Saving in Coal from Expansive Working, the extra Cost of Larger Engines being taken into account ; Boilers, Wheels, or Screw, and Indicated Horse-Power being supposed to remain the same. A N N U A L COST OF COALS T A K E N AT c25 P E R CE~T, OF CAPITAL,
Propor- ~ Propor- ]. . . . . . . . . I ' - - - ~ C o s t of En.'ines alone'-(cxclusive of Boilers, .... tional ] cost tional Screw. &c.~ equal to 15 per cent of eapital, ]} nominal of "Cost of coal Saving in | (as in Australian Vcssels~ Class 4.) / nersccoal for t in per cent* cost of coal | . . . . . . . . . . . . . . . . . / Power, or same age oforigi- in per cent- | l)ermancnt Gross gum on ] size of actu/d nM capital. age of origi- | Increasing the n~l capital. | Nominal IIorse- charge on capital, capital, deduct~ngines. power. | power, adds to being 5 per cert. ing tile a m o u n ~ |capital invested, on addition, in F from D: 1
1'00
1~
"81
2 t ~½
.71 .63
3
"57
1
Per Cent.
Ipe,.'d 'nt.
:5o0
20"25 17"75 15"75
] [
i.go
7'25 9'25
,4.5 fp C
Ce, C ent.
4;i
t 1)
_
P e r Cent.
:J7
15.00 22.50 30.00
•75 1"12 1"50
E
F
Per Cent.
i. s 6.50 8.13 9.25
_
G
202
&leehanics, Physics, and Chemistry.
It is evident that the dearer the coal is, or the larger the quantity consumed in proportion to the actual power developed, the more advantageous would be the saving effected by expansive working, as the per centage of saving in coal would the sooner cover any extra cost of" engin;: ;b:nidn:lr;:O~eg:i~gr2f~:::s cfloe)r~Ys):Wv2h~,~frk~hne si::dOfthtehi; engin " , " ' p " " g, "r cost be consequently doubled, there yet remains a gain, under the worst circumstances, of "15 per cent. Oll capital, and under favorable eircum. stances, such as those presented by the Australian vessels, of 9~ per cent. on capital.* be continued.)
(To
TWENTY-FIFTH
MEETING
OF THE
ADVANCEMENT
BRITISH ASSOCIATION OF
:FOR T H I I
SCIENCE. t
On t}~e Condition of the .3tmosphere during Cholera. By Dr. R. D. T~1oMsoN.--The chemical condition of cholera atmospheres is a question of intense interest in the subject of public health ; but, with the exception of the unpublished experiments of Dr. Prout, in 183"2, comparatively little attention appears to have been bestowed on it. One of the most striking circumstances connected with the occurrence of the disease is, that no change very palpable to the senses prevails, and even one may have remarked that the weather has usually been exceedingly agreeable. In London, at St. Thomas's Hospital, the neighborhood of which afforded a large supply of cholera eases, the relative weight of the air in August, 1854, a cholera month, and in August, 1855, when the metropolis was in an extremely healthy condition, is exhibited in the following table, in grains per cubic foot : - 1854. Weight Week ending August 5 .. " 12 ", " 19 .. " 26 .. Sept. 2 .. " 9 .. Mean
..
of Cubic iF. in grains. 522'9 g r a i n s 526'7 " 595,0 " 523'5 " 525.1 " 530'3 " 525.6
"
1855. W e i g h t of Cublc F t . Week ending in grains. August 4 .. 516.9 g r a i n s " 11 ". 524.3 ,, " 18 .. 525'9 " ,c 25 .. 519.2 '¢ Sept. l .. 523'0 " " 8 ., 531.6 " Mean
..
523"5
"
The result, as deduced from tills table, which has been calculated approximately from the barometric pressure and dry and wet bulb thermometer, is analogous to that obtained by Dr. Prout, in 1832, as the author was informed by himself. Corresponding observations have been made at Greenwich by Mr. Glaisher, and the same conclusions arrived at ; from which it would appear that this superior weight of a given bulk I t has not been considered necessary to i n c l u d e more t h a n the tlve classes of vess e l s i n the tbregoing Tables, although m a n y o t h e r classes exist, in w h i c h the propert i o n a t e cost of coal and m a c h i n e r y vary from the a m o u n t s given. In order, however, t o a s c e r t a i n what a d v a n t a g e s would be gained b y the substitution of larger e n g i n e s in a n y specific case, it will only be neeessalT to substitute the correct a m o u n t s i n place of t h o s e g i v e n above. 1" :From the Lond. A t h c n m u m , September, 1855.