New Forms of Stereometers. 307 



Paalzow, Wiedemann's Annalen, XIII (1881) 332. 



Raikow, Chem. Zeit.^ 1888, 525. 



A curious instrument of this character was also invented 

 by Harting {Archives Neerland, 1872, VII, p. 289), to 

 determine the volume of the air chambers of living fish. 



Notwithstanding the numerous forms of volumenometer 

 which have been described it is curious that none of them 

 has come into general use for density determinations. 



With the object of designing a simple and fairly accurate 

 form of volumenometer, we commenced a series of experiments 

 in the physical laboratory of the Owens College in 1883. 

 It was first of all found that there were so many practical 

 difficulties to be overcome in constructing Kopp's volume- 

 nometer that any idea of employing it as a laboratory 

 instrument had to be given up. The chief difficulty was 

 the construction of a glass cylinder and piston tight to 

 mercury under the pressure of one or two atmospheres. 

 This form of the apparatus was therefore abandoned, and 

 an instrument (which is figured in Stewart and Gg&'s Practical 

 Physics, Vol, I.) constructed on the type of Miller's stereo- 

 meter. The pressure was altered, as in the instruments 

 of Regnault and Miller, by running mercury in and out of 

 the apparatus. This process is very objectionable in an 

 apparatus intended for general use, and, moreover, is liable to 

 error on account of the difficulty of getting rid of air bubbles 

 in the narrow parallel tubes. 



At this point our experiments were interrupted, and 

 were not resumed until the long vacation of 1889. An 

 instrument was then arranged as shewn in Fig. 6. 



A glass tube, about 1 5 mm. in diameter, was constricted 

 at four points, at each of which a cross was etched with 

 hydrofluoric acid. This tube (A) was firmly clamped on to 

 a vertical wooden stand, and was connected by thick india- 

 rubber tubing (B) with a piece of straight tubing (C) which 

 could be moved up and down in a groove, a millimeter scale 



