Class N.]

BALANCES, BY DELEUIL, BERANGEB, SACBE, Ac.

250

socket, in which one of the extreme knife-edges is fixed,moves in a slit in the direction of the length of the beam,and is adjusted in that direction by means of two screws.

A smaller balance is exhibited, of almost exactly thesame construction as the preceding; it is capable (pro-bably) of carrying a kilogramme in each pan. A PrizeMedal was awarded to Mr. Bache.

Deleuil (France , No. 1G0, p. 1178) exhibits a largebalance, capable of carrying two kilogrammes in eachpan. The middle knife-edge rests upon a plane surface ofsteel. The pans are suspended from plane surfaces ofsteel, which rest upon the extreme knife-edge. Screwadjustments appear to be avoided, in order to secure in-variability in the positions of the knife-edges. The cast-iron base of the balance has holes under the extremeknife-edges, for suspending large globes of glass forweighing gases, in an enclosed space beneath the base ofthe balance. Both the construction and workmanship ofthis balance appear to be extremely good.

A chemical balance, by the same exhibitor, capable ofcarrying 3U0 grammes in each pan. The pans are of pla-tinum, suspended by silver wires.

Another chemical balance, capable of carrying 200grammes in each pan; the pans are of platinum.

In these two balances the middle knife-edge rests upona plane surface of steel. The pans are suspended fromslightly curved steel hooks.

Balances of this construction, though considerably infe-rior to that in which the pans are suspended from planesurfaces, are simple, not easily deranged, and accurateenough for all the ordinary purposes of chemistry, forwhich they are expressly constructed.

An assay-balance, of the ordinary construction andexcellent workmanship, is also from the same exhibitor.

A Council Medal was awarded to M. Deleuil.

Collot, Brothers (France , No. 1155, p. 1233) exhibita large balance, capable of carrying two kilogrammes ineach pan. In its construction and excellence of execution,it very closely resembles the large balance of M. Deleuil.

An assay-balance of the ordinary construction is alsoexhibited by Messrs. Collot.

A Prize Medal was awarded to Messrs. Collot.

Beraxgeu (France , No. 7G1, pp. 1216, 1217) exhibits abalance to be placed upon a counter, with platforms forholding the substance to be weighed, and the weights."With fifty kilogrammes in each pan, the addition of onegramme to the weights in either pan causes the index tomove through about a quarter of an inch. When triedwith twenty kilogrammes in each pan it was found to turnvery sensibly on placing half a gramme in one of thepans.

INI. Be'ranger also exhibits a steelyard in which theweight is moved along the arm by a screw of the lengthof the long arm, and parallel to it, having a head of about4 inches diameter, divided into 100 parts. This steelyardis sensible to 100 grammes, with 1,000 kilogrammes sus-pended from the short arm.

Also, bascule en fair, a double steelyard. The end ofthe short arm of a steelyard is connected by a link withthe extremity of a lever, and at a distance from the ful-crum of the lever equal to a small fraction of its length is aknife-edge, from which the substance to be weighed issuspended. One of these, capable of weighing 1,000 kilo-grammes, costs 260 fraucs.

M. Be'ranger exhibits a model of a machine for deter-mining the pressure exerted by each wheel of a loco-motive.

Also, a peso-compteur, a weighing-machine, which re-gisters ou a sheet of paper the weight of every articleweighed. Besides these there are a great many commer-cial balances, all of which are most ingeniously contrived,extremely well made, very accurate, and considering theworkmanship, and the number of adjustments to beattended to, very cheap. Although the Jury consideredthem well deserviug such reward, no Medal was voted toM. Beranger, on account of these being commercial ba-lances, and as such thought by the Jury to belong toinstruments for direct use, rather thau to philosophicalinstruments: thev have, however, received a prize inClass V.

Sacre (Belgium, No. 504, p. 1167,) exhibits a largebalance, capable of carrying two kilogrammes in eachpan. The manner of fixing the extreme knife-edges tothe beam is different from that usually adopted, in whichthe under horizontal surface of the knife-edge is in juxta-position with the horizontal surface of the beam, widenedat that particular part, and firmly fixed to it by one ormore screws. In M. Saerd’s balance, on the contrary, theends of the beam terminate in vertical plane surfaces, towhich are attached, by screws, vertical plates of steel,terminating above in knife-edges. The pans are suspendedin such manner, that their swinging in any direction hasno tendency to twist the beam of the balance.

This instrument is remarkable for the extreme beautyof its workmanship.

M. Sacre also exhibits an assay-balance, in which, con-trary to the usual construction, the pans are suspendedfrom plane surfaces of steel which rest upon long knife-edges, and are supported independently of the beam whenthe balance is not in action : it is therefore not only moreaccurate thau ordinary assay-balances, but is enabled tocany 20 grammes iu each pan without injury. The workis extremely good.

In assay-balances, as usually constructed, the pans aresuspended from hooks, which themselves rest on hooksworked to a fine edge, attached to the ends of the beam,and are not calculated to carry a weight of more thantwo grammes.

A Prize Medal was awarded to M. Sacrd.

A. Oertltxg (Prussia, (No. 87, p. 1053) exhibits abalance of very beautiful workmanship, capable of carry-ing a kilogramme in each pan.

The knife-edges are let into dove-tailed notches in thebeam.* The adjustment of the distance of the extremeknife-edge from the middle knife-edge is effected by meansof a vertical cut in the metal of the beam, which may beslightly widened or contracted by screws. The agateswhich rest upon the extreme knife-edges, and from whichthe pans are suspended, are not plane, but have an obtusere-entering angle, into w hich the less obtuse angle of theknife-edge enters, and are not suspended independently ofthe beam when the balance is not in action.f Two ther-mometers are placed with the bulbs as high as the beam;but it probably would have been better if the bulbs hadbeen placed a little above the scale-pans, for the tempera-ture of the air immediately surrounding the object to beweighed often differs sensibly from that of the air in theupper part of the balance-case.

Oertling has also two smaller balances, of similar con-struction, capable of carrying 100 grammes in each pan.A Prize Medal was awarded to Mr. Oertling.

Beimaxx (Prussia, No. 86, p. 1053). Balance, capableof carrying one kilogramme in each pan. The knife-edges are opposed to agate planes. The adjustment ofthe position of the knife-edges is effected by means of anoblique cut at each end of the beam, the breadth of whichmay either he increased or diminished by screws.* Thisis the only balance in the Exhibition in which a circularlevel has been adopted. The Jury considered it worthyof Honourable Mention.

Hoffmaxx and Eberhardt (Prussia, No. 88, p. 1053)have exhibited balances for apothecaries: they seem wellsuited to the purpose they are intended to serve.

Luhme, J. F., and Co. (Prussia, No. S3, p. 1053) exhibitchemical balances. One of them is capable of carryingone kilogramme in each pan; another of carrying 100grammes in each pan; a third 50 grammes in each pan;and a fourth 25 grammes in each pan.

A Prize Medal was awarded to Messrs. Luhme.

Batka (Austria, No. 135, p. 1014) exhibits a very smallbalance by Kusche, of Vienna , contained in a platinum

* It is doubtful whether this mode of attaching the knife-edge is quite as good as when the beam is made w ider atthe extremities and the middle, and the whole length of theknife-edge rests upon it.

t The form of the agates seems to be objectionable.

j In the present case, too much reliance seems to havebeen placed on this mode of adjustment; for one of thecuts has been w idened by screwing till a crack in the beamlias begun to form.