Heat-production Associated with Muscular Work. 97 



more external wooden shell are placed means by which heat may be added to 

 or subtracted from the zinc box in a graduated fashion so as to annul any 

 such observed differences in temperature. Thus the zinc box is kept in each 

 of its several zones, each zone corresponding to a group of thermocouples, at 

 the same temperature as the copper box, and the thermal insulation of the 

 calorimeter is thus insured. 



The subject of the experiment enters the calorimeter by a window space 

 left in the walls of this nest of boxes, and is then sealed in by glass and 

 wax. The heat produced in his body, as well as the heat into which all his 

 mechanical work is finally converted, raises the temperature (1) of an 

 insulated radiator system through which a steady stream of water is main- 

 tained ; (2) of the calorimeter box ; (3) causes some evaporation of water 

 from his respiratory passages and skin, and (4) tends to raise his own 

 temperature. Each one of these four stores of heat is observed in suitable 

 ways, and the summed account of their alterations provides a measure of the 

 heat-production of, or total transformation of energy in, the subject. 



Now, although the main principles of construction are the same as those of 

 the original calorimeter in the Middletown University, I have altered many 

 small details, in part for the sake of economy, in part for convenience, and in 

 some small degree with a view to improvement. Most of these I hope to 

 describe briefly in a more extended commimication ; to one alone, as some- 

 what modifying the usage of the instrument, I refer at present. This 

 modification consists in the introduction of a source of heat other than the 

 man, in some cases adding substantially to the total heat-production. The 

 main reason for this change in procedure was a desire to follow the progress 

 of changes in the heat-production of the subject more closely than was 

 possible with the original arrangement. 



Whilst endeavouring to follow the events of shorter periods of time, 

 e.g., complete observations every 5 minutes, it was soon found that of the 

 four stores into which the heat produced by the subject was delivered, one 

 alone, the temperature of the calorimeter, had a sufficiently elastic capacity 

 to follow abrupt changes. Associated, however, with the possession of this 

 advantage was the failing that, thus abruptly changed, it tended to form 

 a similarly abruptly changing site of heat leakage, unless rapidly checked by 

 adequate and almost simultaneous adjustments in the temperature of its 

 environment, that is of the enclosing zinc box. On this account it is 

 necessary that modifications in heat-production must be kept well within the 

 limits of adjustment of this process, which by the way may conveniently be 

 termed the balancing of the calorimeter. It is only when such limits are 

 not transgressed that any reliance can be placed upon the value of such 



