260 NEW HYDROSTATIC BALANCE. [June, 



out his characters of the Barita I am at a loss to conjec- 

 ture, for it should seem not to have been the Boat-tail; his 

 words are: subgrisea, humeris coeruleis, remigibus extus 

 viriclibus. Syst. Nat. GmeL 



Report of a Committee on a New Hydrostatic Ba- ^ 

 LANCE, invented by Isaiah Lukensy and submitted to - 

 the Academy, Read May 26th, ISIS, \ 



The undersigned committee beg leave to report, that \ 

 the instrument invented by Mr. Lukens, and referred to | 

 them by the Academy, consists of a very sensible steelyard ] 

 or Roman balance, so arranged as to be particularly adapt- I 

 ed to the finding of specific gravities. The arms of the ba- ^ 

 lance are so constructed, in the first instance, as to be in i 

 exact equipoise, when unloaded. The object [C] of which 

 *• j the specific gravity is to be ascertained is suspended to the ] 

 shorter arm, by any of the usual methods; and its relative ^ 

 weights in air and in water are indicated by the numbers 

 on the graduated arm [A] at which the moveable weight or ' 

 pea [D] is suspended, when the beam is brought into a ho- J 

 rizontal position. It is evident that the absolute weight of i 

 the pea is arbitrary, and it is one of the advantages of the i 

 instrument that the pea may be altered to suit the weight \ 

 of the object under trial; even a stone of a proper size ^ 

 might be employed, and would always be at hand. 



When great accuracy is desired, a second pea is em- < 

 ployed, which must be either one tenth, or one hundredth 

 part the weight (5f the first. The larger pea will then in- '\ 

 dicate the units of weight, and the smaller tlie tenths or ; 

 hundredths. The same object might also be obtained by ] 

 suspending the pea to the middle of a Vernier-scale. 



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