72 Dr. Hare’s Improved Eudiometers. 
Or tHE MercuriaL Surpinc Rop Evpiometer, with A. 
Water GauGe. 
The Eudiometer which | bave des«ribed, though satisfac- 
tory in its results, and in its conveniency, when used with 
water, has not been found so when used over mercury. The 
great weight of this fluid caused the indications to vary in con- 
sequence of variations of position, during manipulation, too 
slight to be avoided. The instrument represented in the fol- 
lowing cut, (fig. 4.) is furnished with a water gauge, which 
being appealed to, enables us to render the density of the 
gases within, in equilibrio with the air without. Hence we 
can effect their measurement with great accuracy. 
Fig. 4, 
