56 Mr. E. H. Griffiths on lie Influence of 



need not refer to them further than to say that the results 

 were most satisfactory. 



When the experiments were in progress the thermometer 

 CD was placed in a hole drilled in the wall of the steel 

 chamber parallel to the side and separated from the inner 

 surface by only -j 1 ^ in.: thus it assumed the temperature of the 

 walls surrounding the calorimeter. Thermometer AB passed 

 within the calorimeter and was immersed to an inch above 

 its bulb in the contained liquid. The reading on the bridge- 

 wire thus gave the difference between the temperature of the 

 calorimeter and the walls of the surrounding chamber. 



To ascertain the actual temperature and the constancy of the 

 temperature of the surrounding walls, a second hole, like that 

 already described, was drilled in the steel, in which a mercury 

 thermometer of open scale was placed. The stem, where it 

 protruded above the lid of the tank, was surrounded by a glass 

 tube up which the motor pumped the tank-water, which, passing 

 out at the top, returned to the tank. The stem, therefore, was 

 maintained at a steady temperature, and the fluctuations ob- 

 served might be considered as solely due to changes in the 

 walls of the steel chamber. The stem of thermometer A (used 

 at the lower temperatures) was divided into millimetres, about 

 27 to a degree, and No. II. (used at the higher) about 20 millim. 

 per degree. They were observed through a telescope con- 

 taining a micrometer-scale giving direct readings to ^ of a 

 millimetre. The tenth of one of these divisions could be esti- 

 mated, and thus changes of toVo° ^- (*• e - aoou ^ '025 millim.) 

 were easily observable. This was important, as the bridge-wire 

 readings had to be corrected for any movement in the tempe- 

 rature of thermometer CD — that is, the temperature of the 

 walls of the chamber. 



The stirrer (which consisted of two nearly vertical narrow 

 paddles, reaching from top to bottom of the calorimeter) was 

 so placed as to throw the liquid across the silver flask and coil 

 against the thermometer. This form of stirrer was not the 

 one I should have adopted had the apparatus been designed 

 solely for the experiments which 1 am now describing. In 

 that case I should have preferred the form described in 

 paper J, which threw the liquid from the bottom to the top 

 of the calorimeter ; and I believe that such irregularities as 

 have presented themselves in these experiments, especially 

 with the smallest mass, are due to insufficient stirring. When 

 the calorimeter is full of liquid the nature of the stirring is of 

 less ( onsequence ; and as I proposed in the experiments for 

 which the apparatus was designed to completely fill the calori- 

 meter, 1 adopted the form which it appeared to me would 



