OF ARTS AND SCIENCES. 



161 



could be made perfectly tight by means of a little white-lead paint. 

 The shafl passed through a stuffing-box at the bottom, which was 

 entirely within the outer surface of the calorimeter, so that the heat 

 generated should all go to the water. The upper end of the shaft 

 rested in a bearing in a piece of brass attached to the cover. In the 

 cover there were two openings, — one for the thermometer, and the 

 other for filling the calorimeter with water. 



From the opening for the thermometer, a tube of copper, perforated 

 with large holes, descended nearly to the centre of the calorimeter. 

 The thermometer was in this sieve-like tube at only a short distance 

 from the centre of the calorimeter, with the revolving paddles outside 

 of it, and in the stream of water, which circulated as shown by the 

 arrows. 



This circulation of water took place as follows. The lower paddles 

 threw the water violently outwards, while the upper paddles were 



Fig. 9. 



prevented from doing so by a cylinder surrounding the fixed paddles. 

 The consequence was, that the water flowed up in the space between 

 the outer shell and the fixed paddles, and down through the central 

 tube of the revolving paddles. As there was always a little air at the 

 top to allow for expansion, it would also aid in the same direction. 

 These currents, which were very violent, could be observed through 

 the openings. 



The calorimeter was attached to a wheel, fixed to the shaft a b, by 

 the method shown in Fig. 9. At the edge of the wheel, which was of 

 the exact diameter of the calorimeter, two screws were attached, from 

 which wires descended to a single screw in the edge of the calorimeter. 

 Through the wheel, a screw armed with a vulcanite point pressed 

 upon the calorimeter, and held it firmly. Three of these arrange- 

 ments, at distances of 120°, were used. To centre the calorimeter, 

 a piece of vulcanite at the centre was used. By this method of 

 suspension very little heat could escape, and the amount could be 

 allowed for by the radiation experiments. 

 vol. xv. (n. s. VII.) 11 



