ACCESSORY APPARATUS. 59 



a second set of weights, and the water, carbon dioxide, and oxygen 

 weighed on a third balance with a third set of weights. 



Other weighings entering into the complete balance of energy, as 

 well as of matter, are the weights of water used to bring away the heat 

 from the apparatus, and in the bomb calorimeter for measuring the 

 energy of income, and the weights used on a platform balance (fig. 46) 

 for weighing a man. With such a system of balances and weights, it 

 is obviously necessary that all weights should be on some standard 

 basis. We have imported from Germany a set of gold-plated weights 

 ranging from i mg. to i kg., and all of our different sets of weights 

 have been carefully calibrated with this set, which is used only for a 

 standard. Consequently all weights used in the experimenting with 

 the respiration calorimeter are reduced to the same basis. The weights, 

 as well as the sensitiveness and accuracy of the balances, are tested 

 periodically every six months and proper adjustments made. 



The individual weights of the standard set have been compared with 

 each other frequently in all possible combinations, and the agreement is 

 in all cases very close. There has been no comparison with any abso- 

 lute standard, as practically all of our work depends upon differences in 

 weight rather than absolute weight. We have, however, no reason to 

 doubt the accuracy of the standard weights as furnished us, for when 

 compared with numerous new sets of analytical weights no noticeable 

 differences have been found. Apparently the analytical weights, though 

 from several manufacturers, must have been referred to standards 

 agreeing very closely with each other. 



With the larger weights used for weighing food and the absorbing 

 apparatus of the respiration chamber, the adjustment was found to be 

 much more readily made if the handle or top of the weight screwed 

 into the base. Accordingly a number of sets of weights were made 

 in the mechanical laboratory of Wesleyan University on this plan, 

 and consequently the work of delicate adjustment is reduced to a 

 minimum. 



For calibrating the larger weights, 200 grams and over, the balances 

 described on page 58 were used, after making all due precautions and 

 interchanging weights from one pan to the other. 



All the weighings and measurements are made at the same level in 

 the calorimeter room, which has an elevation of 48.8 meters above sea 

 level. The latitude of Middletown is 41 34'. It has been found 

 that to correct all weighings to standard gravity, i. e., latitude 45, 

 would involve a large amount of unnecessary labor. The actual cor- 

 rection is only about three parts in 10,000, representing a degree of 

 refinement that is far removed from many of the operations in connection 



