On a Modification of Bunsen's Calorimeter. 171 



cient to justify the inference. From (2) we learn that we may 

 infer that both X and Y or neither of them have happened 

 provided we know that any of the events A, B, C, D (one or 

 more) has happened ; while (3) informs us that the combi- 

 nations AC, AD, BC, BD are impossible. 



Other inferences, besides those required, may easily be 

 drawn, For instance, since 



(ay)' : : x F +y f : : x'lj + xij + x'y' : c f d r , 



we get c + d : my. Similarly we get a + b : x'y' . The product 

 of these two inferences implies (2). 



Where is the formidable array of 6 x 2 6 (or 384) letters 

 which Mr. Yenn, unless I misunderstood his words, supposes 

 the logician obliged to face as a necessary preliminary to all 

 inference in every problem requiring six letters ? Whether 

 Dr. Boole's or Prof. Jevons's method can fairly be charged 

 with imposing this heavy labour I am not prepared to say ; but 

 my method certainly does not impose it. 



Yours &c. 



Hugh M'Coll. 



73 Rue Siblequin, Boulogne-sur-Mer, 

 August 3, 1880. 



XXYI. Note on a Modification of Bunsen's Calorimeter. 

 By W. W. Gee and W. Stroud*. 



PROFESSOR STEWART described to the Manchester 

 Literary and Philosophical Society, on March 4, 1879, 

 a calorimeter devised with the purpose of obtaining the specific 

 heat of a substance of small quantity with much readiness. It 

 consists of a combination of part of Bunsen's arrangement with 

 that of Favre and Silbermann. In it advantage is taken of 

 the method employed by Bunsen — namely, that of dropping a 

 small body, whose temperature does not differ much from that 

 of the atmosphere, into ice-cold water contained in a small tube. 

 In Bunsen's instrument the heat so given up by the body ex- 

 perimented with is measured by the change of volume produced 

 by the melting of ice surrounding the tube. There being cer- 

 tain practical difficulties in the use of this method, it was 

 thought that if the tube were surrounded by a large mass of 

 mercury, forming the bulb of a delicate thermometer, after the 

 manner of Favre and Silbermann, then the direct expansion 

 of the mercury would indicate the amount of heat brought into 



* Communicated by Professor Stewart to the Physical Society, having 

 been read at the Meeting on June 26. 



