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Experiments on solar light
250
Physical Science.
m e n t u m o f the drum, continues it in motion, during the interval when the tension is o f course diminished ? A d m i t t i n g this suggestion to be correct as far as it goes, still there would be an a p p r e c i a b l e dit[erence; it would seem, in the two belts repesented in the cut f o r tile reasons before suggested, besides leaving a considerable portion of t h e strain and pressure to destroy the belt and wear the bearings. One t.hing is certain that whether tile belt be long or shot b one means of securing i t from slipping is to make it shorter. T h e r e i s much justice in tile remarks of Mr. B. that sufficient care is seldotu t a k e n to have belts to run free and easy, and it has been one of the greatest e r r o r s more or less prevalent in all Cotton and Woolen Mills to run the b e l t s so as greatly to injure the belts, and rapidly increase the wear o f t h e bearings--and when belts will so run without slipping upon the drums o r pulleys, they will wear |br a great length of time. For although a belt m a y be heavily loaded, yet, if at every revolution it can have an op. portuu~ty f o r relief f~om its tension, so as to contract to its natural texture, it will p r e v e n t it from breaking by the stress upon it? M a y n o t the belt or'greater length be mo,'e du,'able, chiefly on account of its b e i n g less frequently strained, and bent and straightened in passing round t h e d r u m s or pulleys? One w o r d on the subject of high velocities: Mr. B. says '% belt adheres m u c h better and is less liable to slip when it runs at a quick speed, than a t a slow speed." I have frequently before heard this thing asserted, and h a v e m y s e l f observed something of the kind in a case whe,'e the work done w a s interrupted or irregular. Nt~t b e i n g able at this time to assign any better reason, I attributed it to the g r e a t e r momentums of the moving parts, acting in a degree as a fly wheel. I n the case alluded to a rope instead of a belt was used. Yours~ &c.
Physical
Science.
:By J o a n W'. DRAPe%M. D. Professor of Cbemistry, Hampden Sidney Colleg% ¥ a .
E x p e r i m e n t s on Solar Light.
(Continued from p. 114.)
1 1 5. 1?,if'eels ofl~ght on vegetation. 115. B o t a n i c a l authors have long been aware of the important effects which s o l a r radiations exercise over the eolour of vegetables. A plant, which g r o w s in the dark, is of a pale whitish colour, and of a transparent aspec% possessing norse of that greenness and vigour which is so characteristically d e v e l o p e d on exposure to the sun;its con.~istency is watery, and alt h o u g h its growth may not be stunled, its appearance is very sickly, its s e c r e t o r y actions are not duly performed, and all its vital operations are carried o n in a state of force. There is no longer any evolution of nitrogen from t h e leaves, and consequently no apparent production of oxygen gas. Light, w h i c h seems to act merely as a stimulus on the green organs of v e g e t a b l e s , indirectly bringing about t h e decomposition of carbonic acid, t h o u g h a c c e s s o r y is not however essential to the growth of plants. Sub-
Experiments on ~olar Light. ~erarJean cavities~ and places thr removed from the direct solar ray, have a flora of their own ; a~d in the abysses of the ocean~ at depths to which no solar beam can penetrate~ and where there is a perpetual night, green plants are tbund flourishing. 116. '].'he green colour of leaves~ is presumed to be an immediate rouse. quence of the act of decomposing carbonic acid. (Decandolle phy. des plantes) It appears to me, that there is some obscurity, if not an. actual error, in the view which botanists take of this matter. They suppose, that by the stimulus of light, some portion of the green organ is enabled to decompose that gas, completely, or to accomplish its actual resolution into an equivalent volume of oxygen, with the entire deposition of the carbon in the solid tbrm; that it is moreover this carbon, so deposited, that gives origin to tile green colour, seeing it forms the ehromule verte itself. Much useless ingenuity has been thrown away by some chemists in explaining, how carbon, tile colour of which is black, or a deep Prussian blue, can produce a lively green, and even if their supposing that the modi(yiog action of a yellow tissue spread over it were correct, of which there is much doubt~ considering the thinness of that tissue, aml the lightness of its tint, yet cer. tainly we have no necessity to resort to any such explanation. The deposit is not carbon chemically, it contai~,s both oxygen and hydrogen in unknown proportions. Of all the physical characteristics of a body, colour is the most inefficient, it is even proverbial, that after uniting in a new mode, com. pounds never bear the colours or their constituents ; nay mot% carbon itself is not essentially of a black colour, as the diamond proves. 117. To a deposit of some compound~ in which carbon enters as an tug'redient, we are to reibr the green colonr orleaves, but not to carbon itself: On this point, vegetable physiology has been thrown into error by incorrect intbrmation, as respects the chemical part of the phenomenon. T h e earlier chemists, who did not possess those extremely delicate methods of gas analysis, which are now available, gave wrong evidence in this matter. "l'ltey stated that on exposing a plant to the sunshine, in contact with carbonic acid, the carbon was separated in a concrete state, the oxygen being l e f t ~ b u t s u c h is not the filet; by no known laws can such a change be brought about~ and hence any reasoning based upon it, as to the colour of plants, is irrelevant. For when a plant exposed to the sun decomposes carbonic acid, a certain volume of oxygen disappears at the same time; in lieu of this, and in obedience to the laws which guide the transit of gases through tissues, (3our. Frank. lnst. Vol. XVIII., p. 27) an equivalent volume of nitrogen is surrendered by the plant in return. Sometimes it is carbonic oxide which is absorbed~ sometimes oxalic acid, or other compound of carbon with less proportion of oxygen. I do not here indicate from whence that nitrogen is derived, since botanists assert, that some plants contain no nitrogen at all; it may however exist in their juices, as gas exists in spring water, or may be retained in a compressed state on their surfaces, it is however a remarkable fact, that nitrogen is present, and perhaps not less remarkable, that its presence has hitherto been entirely overlooked. 118. T h e carbon thus taken from the acid, does not pass through the tissue of the leaf in a concrete form, or give rise to a concrete deposit; it bears with it a certain part or the oxygen with which it was fbrmerly united, tim rest being set free; the carbon and oxygen so conveyed into the plant, entering into combination with hydrogen, gives rise to the ehromnle verte; hence we se% that the green colour depends indirectly on the de-
252
Physical Science.
composing action~ that when this goes on without interruption~ that is fully developed. 119. I took five pea plants out of the garden~ as nearly resembling each other in size, and other particulars as might be: they had just appeared above the surface of the earth, and were beginning to put nut leaves. These plants [ designate by the numerals 1, 2, 3, 4, 5. Each one was planted in a small glass vessel, with a hole in the bottom for the pnrp(,se of supplying it with water, after the manner nf a common flower pot. Number 1 was placed in a box, into which light passed which had traversed a solutinn of sulphate of copper and ammonia. No. 2, in a similar box into which light was admitted after having undergone the action of chromate of potassa. No. 3 was placed in the open air. No. 4 in a box, into which light passed which had been transmitted through sulphncyanate of iron. No. 5 was shut up in a dark closet. This arrangement was completed on the second day of May. "With a pair of compasses the height nf each plant was ascertained, and of that~ and of the number of leave% a memorandum was takem In three days time an examination was made. No. 1, had attained three times its former height, and doubled its number of leaves. No. 2, not quite twice its former height, no new leaves, in appearance not so l~lumi:, and transparent as tbrmerly. No. 3, twice its tbrmer size, with no fresh leaves. No. 4, tbur and a half times its former size, and double its number of leaves. No. 5, three and a half times its former size, the leaves looked yellowisb. 120. It is here proper to remark, that the increase of size is not to be taken as an index of any action of the absorbing" medium. Some yearsag% 1 had occasion to notice, that rapidity of growth was greatly influenced by the quantity of aqueous gas in the atmosphere. W h e t h e r the observation possesses any novelty, 1 am not prepared to say, but if any one causes plants to grow in glass vessels, containing the maximum quanti}y of vapour which their atmosphere can hold, at the temperatures under trial, their nnusual increase of dimensions, witl present a strikingly remarkable phenomenon. 12I. In fourteen days, from the commencement of this experiment~ another examination was held. No. 1, all its leaves of a grass green. No. 2, of a darker green. No. 3, green, but n t a bluish tint when compared with a plant taken from the garden. No. 4, ofa hright green. No. 5, pale whitish yellow~ with no fresh leaves, but grown to thirteen times its former height~ nnd apparently in a vigorous condition. N. B . ~ \ V i t h respect to No. 4, tt:e plant under sulphocyanate of iron, I was nnt aware at the time of making this trial, of the singnlar properties of that substance in relation to light~ in the course of a fortnight, which had elapsed~ the solution from being of a deep blond red, had become perfectly cotourless. No reliance is there~bre to be placed on this result. 1~2. Among a number of experiments which were instituted with an intention of illustrating the same point, and which gave analogous resul% it may be mentioned that the seeds of common garden cress, were caused to germinate and grow in the boxes mentioned above. And no matter what was the substance through which the light passed~ the young plants after
~ha
Experiments on Solar Light.
reaching a certain size, were always green,--but those which grew in the dark had yellow leaves and white stalks. 123. The general result of these trials goes to prove, that it is not this or that species of ray, which gives rise to the colour of leaves, the absence of the chemical ray, or of the calorific ray does not appear to affect it, nor have we any direct proof that the colorific ray exercises any influence. Humboldt has stated, that in the mines of Germany, plants as the poa annua, el compressa, plantago laneeolata, &c., grow in recesses where the sun's light never comes, and provided hydrogen gas be present, their colour is green. In the Atlantic ocean he saw a marine plant f urns vitifolius, brought up from a depth of 190 French feet, where according to the calculationsofBouguer, ttlelight was only equal to that emitted ( r o m a c a n d l e at 203 (eet distance~ and yet its colour was green. Decandolle mentions that artificial light, as that of lamps gives the same result; a proof that it is certainly not the chemical and perhaps not the calorific rays which cause the phenomenon. 124. Perhap:s light in this case acts only a~ a kind of stimulus; it wouhl be desirable to make trial of some plants whose leaves are naturally white; of this class there are several indivi(hmls; would they or would they not cause the decomposition of carhonic acid? From many indications it is not improbable that there is a variety of chemical rays, each of which brings about changes of a character appropriate to itself. As yet, we have not learned to di,~ting'uish these from each other, anti are not provided with the means of effecting their separation. A remarkable observation which appears to me to be very much in point, was made many years ago, by Prot. Silliman; it has not obtained that attention which it deserves; he states, that on exposure of a mixture of chlorine and hydrogen to the light of a fire, an ex'plosion was produced. I quote the fact, however, only from memory, and have endeavoured to substantiate it undei' a variety of circumstances, but wifl~ a want of success probably due to the absorbing action of the glass jars used, or to the nature of the light. It is desirable that this experiment should be once more repeated; it would settle an important point, that chemical rays of different characters exist. I have referred to this before in speaking of the perehiliou motion of matter;/br it is more than probable, that there are chemical rays not absorbable by the chromates of potassa. No~rr.~_/h the foregolng papers the reader is requested to make the follo wing covrec. tlons of typographical errors. ERRAT& Sec. line '2 3 8 9 S 19 "25 40 8 40 10 40 16 41 1 41 12 43 o 4:5 5 48 3 4S 6 80 10
instead of coherent same light prism a in the practical glasses with various apertures chemist pressing multiptHe d0°Fall, isometric e -4.- :20 e + (; 26+ N
read. ir~herent sun's light prism d inpractical glasses fig. 19 with narrow apertures chemists /:ailing n,nltiple ll0Fah. isomeric C "t" 2 0 C .~ O 2 0 -{- N
| Sec. line instead of [ 56 7 least 5~3 3 temperature 5~ 3 moveable [ re3 't moveable I 59 ~0 laterna[ 68 11 Sulphocyrate 6S 15 Sulphocyratn I 68 23 platinium [ 69 ~4 ananalysis 71 5 hydrodide [ '72 ') eloride I 9~ 15 zequilibris I 99 4 natural 114 1 wherever
read last temperatures invisible invisible lateral sulphoeyanate sulphocyanate platinmu on analysis hydriot]ide chloride ,'equilibrio internal whenever
Recent Occultations. The immersion of Antares behind the moon's dark limb on the 10th of August last, was observed at several places in and near Philadelphia, as VOL. XX,--No. 4.~OcTOBER~ 1857. ~
Civil Engineering.
254
follow% in mean time of the places of observation. the moon was obscured by clouds, No.
Observer.
Meat~ time.
A t the time of emersion
Latitude.
--7 I 3 / l 4 | 5 / [ 6 f
Assumed Longitude.
i
0 0-TVwToC W.]{ aohns¢n, ~V. H. C. Riggs, J. Gummere, S.J. Gummere
4.2 42 16 44 43
.79 .99 .00 40 .50(
59 5 16 59 I 5 .16 1 12 135 .00 12 1:35 .00
" " " "
l i !
The reductionof these observations after the method o1 Bessel, Astrotmo misehe INachrichten, No. 15I and 155~, has furnished the following results.
~i 3&4
~
-
-31 .41 +' -1.747 - - ---3.o82 --+3.542 35.38 I + 1.747 ~ 3 . o 8 3 +3.544[
t
:~_~!_ __A__'*_..?_<~+_l._r451__-E.°_L °l +A!:~?3L-5h !m !s~._r4
Wher% m = the longitude from Greenwich + E a s t - - West, that wouhl be deduced h-ore the observation if the star's and moon's places as given in the Nautical Ahnanac were fi'ee hom error. ----- the number of seconds of a r e b y which the moon is more or lessadvaneed in its orbit than ils tabular place. = the number of seconds o f a r c b y ~hich the mo(m is north or soutb of its tabular place, measured on a perpendicular to its orbit. ~7 = the eo,'reetion of the moon's tabular horizontal semi-diameter. d = the longitude obtained by applying these corrections, whence d=m + a~ +b~+ or/; assuming, d = - - 5h 0m 40s for the State Hans% Philadelphia~ the observations give, 9." ~26 == a 6 + b ~ + e y/, and for Haverford School d = ~ 3h l m 1.%.74, as above. SE,ARS C. WALKER. September 6th~ 1837.
Civil
Engineering.
•/t short tlistorical and Topographical Sketch of the La Grange and z][emphis Rail.road, Tennessee. By Cr~aar.~s POTTS, C h i e f Engineer L. & M. R.R. T h e La Grange and Memphis Rail.road Company of the State at Tennessee, was incorporated by the Legislature of that State on the 1 4 t h o f December, 1835. T h e charter is tile first of its Idnd granted in this State. T h e capital stock of the company, designed lbr the main stem of the road, is fixed at 300,000 dollars in shares of 100 dollars each~ which may be increased to b00~000 dollars. .At the time the company was incorporated several lateral branch roads w e r e contemplated and connected in the hill; the only one, however~ which has fulfilled the requisitions of the charter, was the branch road from Moscow to the town of Somerville. T o c o n struct this branch the charter allowed an additional sum of 75~000 dollar%
Physical Science.
m e n t u m o f the drum, continues it in motion, during the interval when the tension is o f course diminished ? A d m i t t i n g this suggestion to be correct as far as it goes, still there would be an a p p r e c i a b l e dit[erence; it would seem, in the two belts repesented in the cut f o r tile reasons before suggested, besides leaving a considerable portion of t h e strain and pressure to destroy the belt and wear the bearings. One t.hing is certain that whether tile belt be long or shot b one means of securing i t from slipping is to make it shorter. T h e r e i s much justice in tile remarks of Mr. B. that sufficient care is seldotu t a k e n to have belts to run free and easy, and it has been one of the greatest e r r o r s more or less prevalent in all Cotton and Woolen Mills to run the b e l t s so as greatly to injure the belts, and rapidly increase the wear o f t h e bearings--and when belts will so run without slipping upon the drums o r pulleys, they will wear |br a great length of time. For although a belt m a y be heavily loaded, yet, if at every revolution it can have an op. portuu~ty f o r relief f~om its tension, so as to contract to its natural texture, it will p r e v e n t it from breaking by the stress upon it? M a y n o t the belt or'greater length be mo,'e du,'able, chiefly on account of its b e i n g less frequently strained, and bent and straightened in passing round t h e d r u m s or pulleys? One w o r d on the subject of high velocities: Mr. B. says '% belt adheres m u c h better and is less liable to slip when it runs at a quick speed, than a t a slow speed." I have frequently before heard this thing asserted, and h a v e m y s e l f observed something of the kind in a case whe,'e the work done w a s interrupted or irregular. Nt~t b e i n g able at this time to assign any better reason, I attributed it to the g r e a t e r momentums of the moving parts, acting in a degree as a fly wheel. I n the case alluded to a rope instead of a belt was used. Yours~ &c.
Physical
Science.
:By J o a n W'. DRAPe%M. D. Professor of Cbemistry, Hampden Sidney Colleg% ¥ a .
E x p e r i m e n t s on Solar Light.
(Continued from p. 114.)
1 1 5. 1?,if'eels ofl~ght on vegetation. 115. B o t a n i c a l authors have long been aware of the important effects which s o l a r radiations exercise over the eolour of vegetables. A plant, which g r o w s in the dark, is of a pale whitish colour, and of a transparent aspec% possessing norse of that greenness and vigour which is so characteristically d e v e l o p e d on exposure to the sun;its con.~istency is watery, and alt h o u g h its growth may not be stunled, its appearance is very sickly, its s e c r e t o r y actions are not duly performed, and all its vital operations are carried o n in a state of force. There is no longer any evolution of nitrogen from t h e leaves, and consequently no apparent production of oxygen gas. Light, w h i c h seems to act merely as a stimulus on the green organs of v e g e t a b l e s , indirectly bringing about t h e decomposition of carbonic acid, t h o u g h a c c e s s o r y is not however essential to the growth of plants. Sub-
Experiments on ~olar Light. ~erarJean cavities~ and places thr removed from the direct solar ray, have a flora of their own ; a~d in the abysses of the ocean~ at depths to which no solar beam can penetrate~ and where there is a perpetual night, green plants are tbund flourishing. 116. '].'he green colour of leaves~ is presumed to be an immediate rouse. quence of the act of decomposing carbonic acid. (Decandolle phy. des plantes) It appears to me, that there is some obscurity, if not an. actual error, in the view which botanists take of this matter. They suppose, that by the stimulus of light, some portion of the green organ is enabled to decompose that gas, completely, or to accomplish its actual resolution into an equivalent volume of oxygen, with the entire deposition of the carbon in the solid tbrm; that it is moreover this carbon, so deposited, that gives origin to tile green colour, seeing it forms the ehromule verte itself. Much useless ingenuity has been thrown away by some chemists in explaining, how carbon, tile colour of which is black, or a deep Prussian blue, can produce a lively green, and even if their supposing that the modi(yiog action of a yellow tissue spread over it were correct, of which there is much doubt~ considering the thinness of that tissue, aml the lightness of its tint, yet cer. tainly we have no necessity to resort to any such explanation. The deposit is not carbon chemically, it contai~,s both oxygen and hydrogen in unknown proportions. Of all the physical characteristics of a body, colour is the most inefficient, it is even proverbial, that after uniting in a new mode, com. pounds never bear the colours or their constituents ; nay mot% carbon itself is not essentially of a black colour, as the diamond proves. 117. To a deposit of some compound~ in which carbon enters as an tug'redient, we are to reibr the green colonr orleaves, but not to carbon itself: On this point, vegetable physiology has been thrown into error by incorrect intbrmation, as respects the chemical part of the phenomenon. T h e earlier chemists, who did not possess those extremely delicate methods of gas analysis, which are now available, gave wrong evidence in this matter. "l'ltey stated that on exposing a plant to the sunshine, in contact with carbonic acid, the carbon was separated in a concrete state, the oxygen being l e f t ~ b u t s u c h is not the filet; by no known laws can such a change be brought about~ and hence any reasoning based upon it, as to the colour of plants, is irrelevant. For when a plant exposed to the sun decomposes carbonic acid, a certain volume of oxygen disappears at the same time; in lieu of this, and in obedience to the laws which guide the transit of gases through tissues, (3our. Frank. lnst. Vol. XVIII., p. 27) an equivalent volume of nitrogen is surrendered by the plant in return. Sometimes it is carbonic oxide which is absorbed~ sometimes oxalic acid, or other compound of carbon with less proportion of oxygen. I do not here indicate from whence that nitrogen is derived, since botanists assert, that some plants contain no nitrogen at all; it may however exist in their juices, as gas exists in spring water, or may be retained in a compressed state on their surfaces, it is however a remarkable fact, that nitrogen is present, and perhaps not less remarkable, that its presence has hitherto been entirely overlooked. 118. T h e carbon thus taken from the acid, does not pass through the tissue of the leaf in a concrete form, or give rise to a concrete deposit; it bears with it a certain part or the oxygen with which it was fbrmerly united, tim rest being set free; the carbon and oxygen so conveyed into the plant, entering into combination with hydrogen, gives rise to the ehromnle verte; hence we se% that the green colour depends indirectly on the de-
252
Physical Science.
composing action~ that when this goes on without interruption~ that is fully developed. 119. I took five pea plants out of the garden~ as nearly resembling each other in size, and other particulars as might be: they had just appeared above the surface of the earth, and were beginning to put nut leaves. These plants [ designate by the numerals 1, 2, 3, 4, 5. Each one was planted in a small glass vessel, with a hole in the bottom for the pnrp(,se of supplying it with water, after the manner nf a common flower pot. Number 1 was placed in a box, into which light passed which had traversed a solutinn of sulphate of copper and ammonia. No. 2, in a similar box into which light was admitted after having undergone the action of chromate of potassa. No. 3 was placed in the open air. No. 4 in a box, into which light passed which had been transmitted through sulphncyanate of iron. No. 5 was shut up in a dark closet. This arrangement was completed on the second day of May. "With a pair of compasses the height nf each plant was ascertained, and of that~ and of the number of leave% a memorandum was takem In three days time an examination was made. No. 1, had attained three times its former height, and doubled its number of leaves. No. 2, not quite twice its former height, no new leaves, in appearance not so l~lumi:, and transparent as tbrmerly. No. 3, twice its tbrmer size, with no fresh leaves. No. 4, tbur and a half times its former size, and double its number of leaves. No. 5, three and a half times its former size, the leaves looked yellowisb. 120. It is here proper to remark, that the increase of size is not to be taken as an index of any action of the absorbing" medium. Some yearsag% 1 had occasion to notice, that rapidity of growth was greatly influenced by the quantity of aqueous gas in the atmosphere. W h e t h e r the observation possesses any novelty, 1 am not prepared to say, but if any one causes plants to grow in glass vessels, containing the maximum quanti}y of vapour which their atmosphere can hold, at the temperatures under trial, their nnusual increase of dimensions, witl present a strikingly remarkable phenomenon. 12I. In fourteen days, from the commencement of this experiment~ another examination was held. No. 1, all its leaves of a grass green. No. 2, of a darker green. No. 3, green, but n t a bluish tint when compared with a plant taken from the garden. No. 4, ofa hright green. No. 5, pale whitish yellow~ with no fresh leaves, but grown to thirteen times its former height~ nnd apparently in a vigorous condition. N. B . ~ \ V i t h respect to No. 4, tt:e plant under sulphocyanate of iron, I was nnt aware at the time of making this trial, of the singnlar properties of that substance in relation to light~ in the course of a fortnight, which had elapsed~ the solution from being of a deep blond red, had become perfectly cotourless. No reliance is there~bre to be placed on this result. 1~2. Among a number of experiments which were instituted with an intention of illustrating the same point, and which gave analogous resul% it may be mentioned that the seeds of common garden cress, were caused to germinate and grow in the boxes mentioned above. And no matter what was the substance through which the light passed~ the young plants after
~ha
Experiments on Solar Light.
reaching a certain size, were always green,--but those which grew in the dark had yellow leaves and white stalks. 123. The general result of these trials goes to prove, that it is not this or that species of ray, which gives rise to the colour of leaves, the absence of the chemical ray, or of the calorific ray does not appear to affect it, nor have we any direct proof that the colorific ray exercises any influence. Humboldt has stated, that in the mines of Germany, plants as the poa annua, el compressa, plantago laneeolata, &c., grow in recesses where the sun's light never comes, and provided hydrogen gas be present, their colour is green. In the Atlantic ocean he saw a marine plant f urns vitifolius, brought up from a depth of 190 French feet, where according to the calculationsofBouguer, ttlelight was only equal to that emitted ( r o m a c a n d l e at 203 (eet distance~ and yet its colour was green. Decandolle mentions that artificial light, as that of lamps gives the same result; a proof that it is certainly not the chemical and perhaps not the calorific rays which cause the phenomenon. 124. Perhap:s light in this case acts only a~ a kind of stimulus; it wouhl be desirable to make trial of some plants whose leaves are naturally white; of this class there are several indivi(hmls; would they or would they not cause the decomposition of carhonic acid? From many indications it is not improbable that there is a variety of chemical rays, each of which brings about changes of a character appropriate to itself. As yet, we have not learned to di,~ting'uish these from each other, anti are not provided with the means of effecting their separation. A remarkable observation which appears to me to be very much in point, was made many years ago, by Prot. Silliman; it has not obtained that attention which it deserves; he states, that on exposure of a mixture of chlorine and hydrogen to the light of a fire, an ex'plosion was produced. I quote the fact, however, only from memory, and have endeavoured to substantiate it undei' a variety of circumstances, but wifl~ a want of success probably due to the absorbing action of the glass jars used, or to the nature of the light. It is desirable that this experiment should be once more repeated; it would settle an important point, that chemical rays of different characters exist. I have referred to this before in speaking of the perehiliou motion of matter;/br it is more than probable, that there are chemical rays not absorbable by the chromates of potassa. No~rr.~_/h the foregolng papers the reader is requested to make the follo wing covrec. tlons of typographical errors. ERRAT& Sec. line '2 3 8 9 S 19 "25 40 8 40 10 40 16 41 1 41 12 43 o 4:5 5 48 3 4S 6 80 10
instead of coherent same light prism a in the practical glasses with various apertures chemist pressing multiptHe d0°Fall, isometric e -4.- :20 e + (; 26+ N
read. ir~herent sun's light prism d inpractical glasses fig. 19 with narrow apertures chemists /:ailing n,nltiple ll0Fah. isomeric C "t" 2 0 C .~ O 2 0 -{- N
| Sec. line instead of [ 56 7 least 5~3 3 temperature 5~ 3 moveable [ re3 't moveable I 59 ~0 laterna[ 68 11 Sulphocyrate 6S 15 Sulphocyratn I 68 23 platinium [ 69 ~4 ananalysis 71 5 hydrodide [ '72 ') eloride I 9~ 15 zequilibris I 99 4 natural 114 1 wherever
read last temperatures invisible invisible lateral sulphoeyanate sulphocyanate platinmu on analysis hydriot]ide chloride ,'equilibrio internal whenever
Recent Occultations. The immersion of Antares behind the moon's dark limb on the 10th of August last, was observed at several places in and near Philadelphia, as VOL. XX,--No. 4.~OcTOBER~ 1857. ~
Civil Engineering.
254
follow% in mean time of the places of observation. the moon was obscured by clouds, No.
Observer.
Meat~ time.
A t the time of emersion
Latitude.
--7 I 3 / l 4 | 5 / [ 6 f
Assumed Longitude.
i
0 0-TVwToC W.]{ aohns¢n, ~V. H. C. Riggs, J. Gummere, S.J. Gummere
4.2 42 16 44 43
.79 .99 .00 40 .50(
59 5 16 59 I 5 .16 1 12 135 .00 12 1:35 .00
" " " "
l i !
The reductionof these observations after the method o1 Bessel, Astrotmo misehe INachrichten, No. 15I and 155~, has furnished the following results.
~i 3&4
~
-
-31 .41 +' -1.747 - - ---3.o82 --+3.542 35.38 I + 1.747 ~ 3 . o 8 3 +3.544[
t
:~_~!_ __A__'*_..?_<~+_l._r451__-E.°_L °l +A!:~?3L-5h !m !s~._r4
Wher% m = the longitude from Greenwich + E a s t - - West, that wouhl be deduced h-ore the observation if the star's and moon's places as given in the Nautical Ahnanac were fi'ee hom error. ----- the number of seconds of a r e b y which the moon is more or lessadvaneed in its orbit than ils tabular place. = the number of seconds o f a r c b y ~hich the mo(m is north or soutb of its tabular place, measured on a perpendicular to its orbit. ~7 = the eo,'reetion of the moon's tabular horizontal semi-diameter. d = the longitude obtained by applying these corrections, whence d=m + a~ +b~+ or/; assuming, d = - - 5h 0m 40s for the State Hans% Philadelphia~ the observations give, 9." ~26 == a 6 + b ~ + e y/, and for Haverford School d = ~ 3h l m 1.%.74, as above. SE,ARS C. WALKER. September 6th~ 1837.
Civil
Engineering.
•/t short tlistorical and Topographical Sketch of the La Grange and z][emphis Rail.road, Tennessee. By Cr~aar.~s POTTS, C h i e f Engineer L. & M. R.R. T h e La Grange and Memphis Rail.road Company of the State at Tennessee, was incorporated by the Legislature of that State on the 1 4 t h o f December, 1835. T h e charter is tile first of its Idnd granted in this State. T h e capital stock of the company, designed lbr the main stem of the road, is fixed at 300,000 dollars in shares of 100 dollars each~ which may be increased to b00~000 dollars. .At the time the company was incorporated several lateral branch roads w e r e contemplated and connected in the hill; the only one, however~ which has fulfilled the requisitions of the charter, was the branch road from Moscow to the town of Somerville. T o c o n struct this branch the charter allowed an additional sum of 75~000 dollar%