An account of the erection of the herschel obelisk rat the cape of good hope accompanied by the report of Col. Lewis, and a plan of the same

dtccount oJ'the Erection o]'the Herschel Obelisk.

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brass tables have a peculiar sharpness of tone, which can be accounted for, in some measure, wl]eu it is considered that they are very different from the sounds produced by the teeth of the wheel itself; in the dead 2 beat escapement the teeth have a sliding motion in the moment o f drop, but not impuise, for it is well known that that is subsequent to the souud. By such application it is proposed to obtain sound so loud as to be dislinet in the stormiest night; but as the constant connexion of such apparatus would neither be desirable as concerns the action of the clock, nor pleasant to the ear as a companion, a mode lias been introduced of readily detaching it altogether. By a certain method, which shall be explained, the hammers are raised from the tables a t one end, and the arms at the other entirely disengaged from the anchor at the pallet, without inconvenience, or disturbing the action of the clock itself. The apparatus within is immediately, and at pleasure, acted upon through the agency of a bolt, which is placed vertically, immediately over the sixty minutes, or about two inches bacl<, sutliciently long to reach a spring of hard brass, which is about half an inch wide, and which passes transversely over the frame work of the clock, and is fixed securely to the back board of the clock ease. Now the mode in which the spring unites its action with the rest of the apparatus is by slight cross-bars, which extend to the extremities of the sides of the frame, so that the ends are immediately over the hammers, with which they are connected by silk threads. Therefore, by pressing down the bolt before named, the hammers are allowed to fall into action, and do their duty simultaneously with the teeth of the wheel upon the pallets. While the little hammers are in action, the teeth el'the wheel are no longer heard. The Astronomer Royal declares by letter, that he has e x a m i n e d l h e plan, and is enabled to say that it answers completely for its proposed purpose; aml that it appears likely to be very useful. Moreover, that the rate of the clock will not necessarily be disturbed during the time of its c o n n e x i o n - - t h o u g h that will greatly depend on certain

eonditions.--( P,.oe. ~slron. See., Lond.) Lond. Athentotlm,

~qn deeou;~t of the ~reetion of the Herschel Obelisk at the Cape of Good HoiJe, accompanied by the Report o f Col. Lewis, and a Plan of the same. By "l'1io~t.~s MACLEAlb Esq. The following is an abstract :--Sir John Herschel, during his residence at the Cape, was President of the South African Literary and Scientific Institution. When he was about to leave the colony, the members expressed a desire to present him with some token of-remembrance ; and, at a full meeting, a few days before his departure, a gold medal was presented, with the impress of the Institution on one side, and a suitable inscription on the reverse. The feelings excited on that interesting occasion strongly evinced how much the members regretted the loss of their president, and their admiration o f one whose talents place him so far above ordinary men, and whose 24,

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~echanica, P&V~cs, and ~/~mist~.

private li(e was a pattern of every domestic virtue. The sum subscribedhaving exceeded the expense of the medal, another subscription list was opened, with the intention of raising a fund for the pl~rpose of placing a substantial structure on the site of the twenty feet reflector in the garden of Sir John's late residence at Feldhausen. Tile proposal was accordingly laid before Sir George Napier, who entered warmly into tile project, and placed his name at the head .')f tile list annexed to a handsome subscription. In the course of a few days the sum subscribed amounted to 190/. At a general meeting, held oil the 28th of November, 1838, the erection of the obelisk was finally determined on ; and a committee was appointed to carry its erection into effect. A. fruitless attempt to procure a granite column at the Cape, of proper workmanship, and within the resources of the committee, ied-to the adoption of a suggestion, that one of Craig|eith stone, from the quarry near Edinburgh, might be obtained without dilfieutty, and of superior finish. A resolutiotx was aecordiugly passed by the ,:ommittec, which, together with a plan of the proposed obelisk, was lbrwarded to Professors Forbes and Henderson, of Edinburgh, wittl :t request that those gentlemen would kindly undertake the necessary superintendence of the work ; a request to which they acceded with a l a c r i t y , ~ a n d the obelisk, in packing eases, arrived in Table Bay in the month of _,kugust, 1841, where it was satbly landed, trader the guidance of Col. Lewis. The following is the report of Colonel Lewis on the erection :~,, In excavating the foundatioti, which was of black gand, it was found m;cessary to go down 4 feet 10 inches, to arrive at lhe iron StOlm gravelly bed, tim substratt~ru of tile country about Feldhauseu. The masonry foundation was formed of concrete, built up in courses of 12 or 14 inches, and composed of iron stone, gravel, and li.ne mortar, well grouted together. On this masonry bed a granite platform t, feet 6 inches square was laid, and the small column fixed by Sir John t l e r ~ h e t on the site of the 20 feet reflector. This mark was removed |'or a few days, in order to bring the masonry foundation to a proper height, but the mark was relaid with mathematical correctness by Lieut. Laffau, Royal Engineers. Previously, however, to relaying the Herschel mark, the suggestion of the committee of construction was adopted of placing tinder it several silver and copper coins, a few inscription medals, and medals of the South African Institution. struck in silver for the occasion; and on the obverse were engraved some notices, statistical and geographical, of the colony; the discoveries of Capt. Ross in the South Polar Regions in 1841, and the operation of remeasuring the arc of the meridian in 184~. These subjects were beautifiltly executed by Mr. Piazza Smyth, assistant astronomer, and hermetically scaled in glass bottles. Also there were deposited a map of the eotony, and engravings of nebulm, observed at Slough, from 18~5 to lSa3, by Sir John Herschel, and a plan of Mr. Maclear's triangulation, connecting the site Feldhausen with the Royal Observatory, and the site of La Caille's observatory, in Strand street, Cape T o w n . Tim bottle was carefully :fixed in a block of leak wood, scooped out on purpose. Vihen the:granite platform was brought ta

Energiatgpe, a new Photographic ~Procees.

2~3

its level, and the Hersehei mark refixed and filled in with eemetlt, i t was necessary to erect heavy shears of large spars, to place the stolI~a of tlle obelisk, composed of large blocks of Craigteith stone, sot~te weigtfing two tons. Tiffs was accomplished with some trouble a r i d expense, and the base of the obelisk was laid with the faces c o r t e s . l)onding with the four cardinal points. The whole was completed o t i the 15til of February, 1842, in presence of some of the c o m m i t t e e , and several of the subscribers and fl'iends of Sir ,lohn Herschel, w h o attended on the oeeasion of placing the top stone of the obelisk. T h e obelisk has the base 6 ii~ct square by 6 feet iu height, and tile p y r a midal part stands 1~? feet above the base. On the east face is a n opelfing showing the ltersehel mark, designatiag Iho aite of the 2 0 feet reileetor. The opening wilt be dosed with a bronze plate, c o n taiui~g the inscription of the purpose for which the obelisk is erected.,, ~ P r o c . ,,,tslrom See., Lend. Ibid. ],2ne~),¢i(~dyt;e, a new P/telegraphic Proce,gs.

B~j Ro1~Fm'r Hu~'r.

While pursrting some investigations, with a view to determine tile influence of the solar rays upon precipitation, I have been led to t h e discovery ef a new p}lotographic agent, which can be employed iu the preparation of paper with a facility which no other sensitive p r o eess possesses. ]Icing desh'ous of affording all the in.formatiou .t possibly can to lhose who are anxious to avait themselves of t h e advautages offered by photography, I solicit a little space in y o u r columns ibr the purpose of publishing the particulars of this n e w process. All th~ photographic p'oc¢sses with which we are at p r e sent aequain{ed, sufficiently sensitive tbr the fixation of the images o[" the camera obsenra, require the most caretitl and precise manipulation; consequently, those who are not accustomed to the niceties o f experimental pursuits, are frequently annoyed by l'ailures. The t¥)llowing statement will at once show the exceeding simplicity o f t h e new discovery. Good letter paper is first washed over with the following solution : A saturated solulion of sueeinie acid, 2 drachms. Mucilage of gum arabic, ~ " Water, 14 " When the paper is dry, it is washed over once with an argentine s o ]tttion, consisting of one drachm of nitrate of silver to one ounce, o f distilled water. The paper is allowed to dry in the dark, and it is fit for use. It can be preserved in a port-folio, and at any time e m ployed in the camera. This paper is a pure white, and it retains its color, which is a groat advantage. At present I find it necessary to expose this prepared paper in the eamera obseura for perioda v a r y i n g with the quamity of sunshine, from two Io eight minutes, a l t h o u g h , from some results which I have obtained, I am satisfied that, b y a nice adjustment of the proportions of" the materials, a much s h o r t e r exposure will sutliee. When the paper is removed from the c a m e r a , no trace of a picture is visible. We have then to mix together o n e