5S4j Royal Society, 



Equivalent of Heat," and the object of the present paper is to advance 

 fresh proofs of its existence, and to give to it the numerical accuracy 

 requisite to fit it as a starting-point for further incjuiries. 



In carrying out the above design, the author has determined the 

 relation of work done to heat produced in the cases of the friction, — 

 1st, of water; 2nd, of mercury ; and 3rd, of cast iron. 



In the experiments on the friction of the fluids, the liquid was 

 contained in a covered cylindrical vessel of copper or iron, and the 

 agitation was effected by vanes of brass or iron, fixed to a vertical 

 axis revolving in the centre of the vessel, whilst fixed vanes pre- 

 vented the liquid being whirled in the direction of rotation. In the 

 experiments on the friction of solids, a disc of cast iron was rotated 

 against another disc of cast iron pressed against it ; the whole being 

 immersed in a cast-iron vessel filled with mercury. 



The force expended was measured by the descent of the weights 

 employed in rotating the apparatus ; and great care was taken to 

 correct it for the friction of the axes of the pullies employed, &c. 



The heat evolved by the friction was measured by exact thermo- 

 meters, and very laborious precautions were taken in order to elimi- 

 nate the effects of radiation or conduction of heat to and from the 

 surrounding atmosphere. The corrected thermometric effect was 

 then reduced to a known capacity for heat, by means of extensive 

 series of experiments made in order to ascertain the specific heat of 

 the materials in which the thermometric effect was observed. 



In this way the number of units of work, estimated in pounds one 

 foot high, required to be done in order to develope one degree Fahr. 

 in one pound of water taken at about 50°, was found to be as 

 follows : — 



772*692 from friction of water, a mean of 40 experiments. 

 774''083 from friction of mercury, a mean of SO experiments. 

 774'-987 from friction of cast iron, a mean of 20 experiments. 



"On the Nitrogenous Principles of Vegetables as the sources 

 of artificial Alkaloids." By John Stenhouse, F.R.S. 



After observing that there are i'evf departments in organic che- 

 mistry which during the last six or seven years have attracted more 

 of the attention of experimenters than the artificial formation of the 

 alkaloids, and attributing this fact to the interesting nature of this 

 class of bodies both as regards their well-defined chemical properties 

 and the important medical virtues which many of them possess, the 

 author proceeds to state, that although attempts to form the natural 

 alkaloids, such as quinine, cinchonine, &c., by artificial means have 

 hitherto been unsuccessful, yet chemists have been enabled by various 

 processes to procure artificially a considerable number of true alka- 

 loids very analogous to those which occur in nature. The various 

 methods by which this has been effected, such as by acting on essen- 

 tial oils with ammonia, by the destructive distillation of coal and 

 animal substances, &c., are then enumerated and described. 



It is also remarked as somewhat singular, that while so many other 

 sources have been examined, no attempt should have been made to 

 procure alkaloids from vegetable albumen, fibrine, caseine, &c., which 



