430 HENRY A. EOWLAND 



when necessary, the paper could be changed without stopping, and the 

 experiment thus continued without interruption. 



The Frame and Foundation 



The frame was very massive and strong, so as to prevent oscillation; 

 and the whole instrument weighed about 500 pounds as nearly as could 

 be estimated. It was placed on a solid brick pier, with a firm founda- 

 tion in the ground. The trembling was barely perceptible to the hand 

 when running the fastest. 



The Engine 



The driving power was a petroleum engine, which was very efficient 

 in driving the apparatus with uniformity. 



The Balance 



For weighing the calorimeter, a balance capable of showing the 

 presence of less than T \ gramme with 15,000 grammes was used. The 

 weights, however, by Schickert, of Dresden, were accurate among them- 

 selves to at least 5 mg. for the larger weights, and in proportion for 

 the smaller. A more accurate balance would have been useless, as will 

 be seen further on. 



Adjustments 



There are few adjustments, and they were principally made in the 

 construction. 



In the first place, the shafts ab and ef must be in line. Secondly, 

 the wheels rrm must be so adjusted that their planes are vertical, and 

 that the tapes shall pass over them symmetrically, and that their edges 

 shall be in the plane of the wheel Id. 



Deviation from these adjustments only produced small error. 



(c.) Theory of the Experiment 

 1. ESTIMATION OF WORK DONE 



The calorimeter is constantly receiving heat from the friction, and 

 is giving out heat by radiation and conduction. Now, at any given 

 instant of time, the temperature of the whole of the calorimeter is not 

 the same. Owing to the violent stirring, the water is undoubtedly at 

 a very uniform temperature throughout. But the solid parts of the 

 calorimeter cannot be so. The greatest difference of temperature is 

 evidently soon after the commencement of the operation. But after 



