On the Mechanical Equivalent of Heat. 



increased to 180° the quantity for any power would be diminished to- 

 one-sixth of that for a rise of 30°, so that any leakage would become- 

 six times the relative importance. 



5. Some means by which assurance of the elimination of the radia- 

 tion and conduction could be obtained, as with a temperature of 

 140 F. above the laboratory these would probably amount to 2 or & 

 per cent, of the total heat. 



6. Scales for greater facility and accuracy in weighing the water 

 with a switch actuated by the counter. 



7. A pressure gauge or barometer by which the standard for the- 

 boiling points might be readily determined at 3° or 4° F. above and 

 below the boiling point, so as to admit of ready and frequent correc- 

 tion of the thermometers used for identifying the temperature of the 

 effluent water. 



8. Some means of determining the terminal differences of tempera- 

 ture and quantities of water in the brake, which would be relatively" 

 six times as large as with 30° rise. 



These preliminary designs apparently demonstrated the practic- 

 ability of the appliances, and also the possibility of their inclusion in 

 the already much occupied space adjacent to the brake. But there 

 remained still much to be done in the way of experimental investiga- 

 tion in order to obtain the data for proportioning the appliances. 



In July, 1894, Mr. Moorby having undertaken to devote himself to* 

 the research, the experiments necessary for the appliances were at 

 once commenced, and these, together with the construction of the- 

 appliances and then standardising, and preliminary experiments; 

 while this was in progress, occupied till February, 1896, when Mr. 

 Moorby commenced the main experiments which were continued into» 

 July, 1896. 



In these expei'iments the time of running was 62 minutes ; the- 

 speed 300 revolutions a minute, on the speed gauges. Observation, 

 of speeds, of the temperature of the in-flowing and effluent water, ana 

 of the temperature of the air were made every two minutes. Obser- 

 vations of the slope of the temperature of the shaft were made every 

 eight minutes. 



The temperature of the inflowing water varied from 32-5° to 34°,. 

 and that of the effluent from 210° to 214° F. The effluent water was. 

 cooled to 8*5° before entering the tank on the scales, in which it was 

 weighed, weighings being taken before and after each trial. 



The temperature of the metal surface of the brake was sensibly 

 the same as that of the effluent water (212°), and, by taking the 

 difference in the work absorbed in two trials and the differences in? 

 the heats developed, the errors of radiation and balance in the brake 

 were approximately eliminated ; and in order to complete the elimina- 

 tion the coefficient of radiation was approximately determined, so that a- 



