464 Royal Society : — Dr. A. Dupre and P. J. M. Page on the 



of the velocity, but found that this law did not fit the results at all. 

 A resistance varying as the cube of the velocity was then tried, and 

 found very nearly to agree with the results of observation ; and the 

 agreement became, we may say, perfect when the assumed initial 

 velocity was slightly corrected. 



As the calculations and experiments were all made without any 

 notion of the resulting law, and without any knowledge of the work 

 already done by Professor Helie and Professor Bashforth, they afford 

 a remarkable confirmation of the results obtained by those gentlemen. 

 This is the more worthy of notice, as their data belong to pieces of 

 large calibre, and the author's to small arms. 



April 30. — Lieut. -General Sabine, President, in the Chair. 

 The following communication was read : — 



"The Specific Heat of Mixtures of Alcohol and Water." By A. 

 Dupre, Ph.D., Lecturer on Chemistry at the Westminster Hospital, 

 and F. J. M. Page. 



The authors have examined a number of mixtures of alcohol and 

 water. They show that the specific heat of these mixtures, up to 

 an alcoholic strength of about 36 per cent., is higher than the spe- 

 cific heat of water itself. 



Two methods were employed for estimating the specific heat, exactly 

 opposite in principle. 



The first consisted in heating a metallic weight to a certain tempe- 

 rature in a steam-oven, similar to that employed by Regnault in his 

 researches, and then plunging it into the liquid the specific heat of 

 which was to be estimated. The rise in the temperature of equal 

 quantities of different liquids, produced by the introduction of the 

 same weight heated to the same temperature, is inversely propor- 

 tional to the specific heat of such liquids. 



Two weights and several calorimeters of different sizes were used. 

 One of the weights was made of brass, and weighed 246*49 grms.; the 

 other was of copper, gilt, weighing 614"49 grms. Both weights were 

 made in the form of stout rings ; and in the inner cylindrical opening 

 of each a small fan-wheel was inserted. 



These rings, after being heated and let down into the calorimeter, 

 were attached to a strand of worsted, and held freely suspended in 

 the liquid of the calorimeter. The worsted had previously been 

 twisted, and when now allowed to untwist it causes a rapid rotation 

 of the ring. The fan-wheel fixed inside the ring thereby produces 

 a current, which, passing through the ring, not only serves to mix 

 the liquid thoroughly, but also considerably facilitates the rapid 

 cooling of the weight. 



The calorimeters, as usual, consisted of cylindrical vessels made of 

 very thin polished brass, supported on stretched silk cords, and sur- 

 rounded by a double cylinder of tin-plate to prevent, as far as possible, 

 any gain or loss by radiation. 



