156 Intelligence and Miscellaneous Articles. 



of 17 kilogr., and the other of 22. These weights descended near 

 two graduated rules. I have deducted from the calculated work 

 (1) the work equivalent to the vis viva retained by the weights at 

 the end of their fall, (2) the work consumed by the friction of the 

 strings against the handle and in the pulleys. 



On the other hand, I estimated as exactly as possible the heat 

 developed by the cushions, — first by employing a good mercurial 

 thermometer, and then by means of a thermoelectric pile compared 

 with the preceding indications, and measuring approximately the 

 specific heat of the cushions and the disk, taking into consideration 

 the losses in the air. The quantity thus obtained was likewise de- 

 ducted from the calculated work. 



Finally, to measure the electrolyzation, I took two large test- 

 tubes, graduated and furnished with platinum wires extending to 

 their bottom, one of which was connected with the machine, while 

 the other was in communication with the earth. These tubes were 

 immersed in a large receiver containing acidulated water, and united 

 by means of a long string wetted to serve as a conductor to the 

 electricity without producing sparks. 



The following are the mean results obtained in twenty-eight 

 operations : — 



Result of twelve operations. 



Hydrogen Calories of Work Mechanical 



disengaged. dissociation. expended. equivalent, 

 gramme. kilogr. 



0-017 0-578 272-84 471*99 



Result of seven operations, 

 0-042 1-428 649-74 455-00 



Result of nine operations. 

 0-005 0-170 79-5 467-64 



Mean equivalent . 464-87 



I should be glad to have these results controlled by other phy- 

 sicists. — Bibliotheque Universelle, Archives des Sciences Pliys. et Fat. 

 Nov. 1873, pp. 252, 253. 



ON THE EXPANSIBILITY OF EBONITE BY HEAT. 

 BY F. KOHLRAUSCH. 



Accidentally repeated observations that ebonite lids stuck fast in 

 glass vessels, or even cracked them, led me to the idea that this 

 material might have a considerable expansibility by heat. Expec- 

 tation was exceeded by reality ; for it was found to be about three 

 times as expansible as zinc. 



The coefficient for 1° was found to be 



0-0000770 measured between 16°-7 and 25°-3, 

 0-0000842 „ „ 25°-3 „ 35°-4. 



