Manchester Memoirs, Vol. xlii. ( 1 898), No. 0, 2 1 



in all the trials, a record being kept ; so that, should any 

 means of determining more definitely the relative slopes 

 of temperature in the shaft be found, it could be used 

 retrospectively. 



Such a means of determining the relative slopes of 

 temperature in the shaft between the stuffing-box and the 

 near brass was obtained by sweating brass thermometer 

 tubes, radiating outwards, on to the end of the stuffing-box 

 and on to the brasses of the near bearing. It appeared to 

 the author that these thermometers, although they did not 

 indicate the temperature of anything in particular, would 

 serve, the conditions being steady, by the difference of 

 their readings to identify similar conditions as to slopes 

 of temperature, and this turned out to be the case. A 

 flood of light was thrown on to conditions which before 

 had been hardly perceptible, and it became possible to 

 observe the smallest differences in the slopes of tempera- 

 ture, thus ensuring the elimination of the conduction of 

 the shaft (which had threatened to be a considerable, and 

 the only considerable, source of error) to within 0'00002 

 of the heat in a single trial, and altogether negligible on 

 the mean of 42 trials. 



In order to relieve Mr. Hall, who had charge of the 

 engines, from the necessity of maintaining the speed 

 constant, a hand brake was arranged on one of the pulleys, 

 by which the speed could be adjusted by one of the 

 assistants, so as to keep the speed within something like 

 0"3 %. And the quantities of water in the brake for 

 various loads and speeds having been ascertained by 

 experiments, the terminal errors were obtained from the 

 records of the initial and final speeds and temperatures. 



The method of conducting the trials was designed to 

 secure the most perfect elimination possible of the heat 

 lost by radiation, and with this view, after the experience 

 obtained in preliminary trials, it was arranged that all trials 



