(770 ) 
Physics. — “Application of the Baroscope to the Determination of 
the Densities of Gases and Vapors.” By Artnur W.~Gray. 
(Preliminary Notice.) (Communication No. 94a from the 
Physical Laboratory at Leyden by Prof. H. KAMERLINGH ONNES). 
For determining the densities of gases, especially while flowing 
continuously, the principle of the baroscope has been variously 
applied by Firzerraip*), LOMMEL *), SmeerT and Dirr*), Musians*), 
Precut’), and others. In the apparatus here described the aim has 
been great sensitiveness combined with simplicity, ease of operation 
and small volume. 
reg a 
0 5 10. 
The accompanying figure illustrates the essential features. A capillary 
glass tube carries at one end a closed bulb, and at the other a 
henuspherical shell of the same diameter, weight, and kind of glass. 
This is fastened to a horizontal quartz fiber stretched on a glass 
frame, and carries a small mirror M, so that rotations about the 
quartz fiber®) as axis can be measured with telescope and scale. 
The whole is placed within a glass tube containing a sensitive ther- 
mometer of some sort, and communicating with a manometer. 
1) G. WP, Firzeeratp. Worlschritte der Physik 41, 102, 1885. 
2) E. Lommer. Wied. Ann. 27, 144, 1886. 
3) A. Siegert and W. Dürr. Zs. f. Instr.k. 8, 258, 1888. 
5) M. Mesrans. Comptes Rend. 117, 386, 1893. 
5) H. Precut. Zs. f. Instr.k. 13, 36, 1893. 
6) The use of the quartz fiber was suggested by the delicate chemical balance 
of Nernst and Rirsenrerp, Beibl. 28, 380, 1904, to which Prof. KAMERLINGH ONNES 
had drawn my attention. Much more delicate instruments are, however, the quartz 
thread gravity balance of Turetirat, and Potnock R. 8. Trans. 193, A, 215, 1900, 
and the magnetograph of Warson, Proc. Phys. Soc. London, 19, 102, 1904. 
