354 Scientific Proceedings, Royal Dublin Society. 



For the purpose of determining the specific gravities of solids, 

 I use a little claw for supporting the substance under water, 

 which can be suspended by a fine wire from a hook beneath 

 the pan. The substance is first weighed in the pan, the claw being 

 attached and immersed in a vessel of water placed beneath. On 

 transferring the substance to the claw an increased weight will be 

 required for equilibrium ; the increase is obviously the weight of 

 displaced water. 



It is observable in the hydrostatic balance that, when the float 

 is about to descend, the system is one of unstable equilibrium. 

 The descent of the float is accompanied, in fact, by decreased dis- 

 placement in the liquid due to the emergence of the wire, the 

 effect being similar to that of an ever-increasing downward pull 

 upon the float : once started, it tends to descend to its lowest point. 

 If we provide a second wire, similar to the emerging wire, ex- 

 tending downwards, and dipping into a vessel of water, as occurs 

 in the operation of determining specific gravity, the effect is in all 

 cases obviously annulled. The correction is, however, with wire of 

 the diameter 0*09 mm., quite unnecessary ; the displacement of one 

 centimetre of this wire representing but a small fraction, 0-06 of a 

 milligramme. 



I state these particulars at length, as I do not at present know 

 of any other weighing machine in which a similar degree of deli- 

 cacy may be so combined with the qualities of inexpensiveness and 

 compactness, up to any ordinarily required power, as in this 

 balance. 



