346 Journal of Agricultural Research voi. v, No. s 



of the coil, and the amperage of the current is measured by a milliam- 

 meter in series with it, the readings of both meters being recorded every 

 minute, or oftener. 



In a 2-hour test in January, 191 5, the total heat production was 139.00 

 Calories, while the quantity measured with the calorimeter was 139.04 

 Calories. Such absolute agreement is not to be expected invariably, 

 though with the conditions ordinarily prevailing in an electric check the 

 two values should not differ by as much as i per cent. A discrepancy 

 of that size would indicate need of attention to some part of the apparatus, 

 or lack of attention to some details of operation. For example, in a 

 3-hour test in February, 191 5, the total quantity of heat generated in 

 the chamber was 370.19 Calories and that measured by the calorimeter 

 was 377.39 Calories. The discrepancy between the two values was due 

 to a considerable decrease in the temperature of the walls of the chamber 

 during the last half of the first hour, resulting from a lowering of the 

 temperature of the water entering the heat absorber. In the two hours 

 following that the heat production was 245.87 Calories, as computed, and 

 246.75 Calories, as measured, a discrepancy of less than 0.4 per cent. 

 The results in the first hour illustrate the statement made on page 340 

 regarding error in heat measurement when the temperature of the copper 

 wall changes so quickly that its thermal conditions differ from those of 

 the iron structure to which the wall is attached. 



LITERATURE CITED 



(i) Atwater, W. O., Benedict, F. G., et al. 



1899. Experiments on the metabolism of matter and energy in the human body. 

 U. S. Dept. Agr. Office Exp. Sta. Bui. 69 (rev. ed.), 112 p., 87 tab. 



[902. Experiments on the metabolism of matter and energy in the human body, 

 1898-1900. U. S. Depc. Agr. Office Exp. Sta. Bui. 109, 147 p., 151 tab. 



(2) 



(3) 



1903 . Experiments on the metabolism of matter and energy- in the human body, 

 1900-1Q02. U. S. Dept. Agr. Office Exp. Sta. Bui. 136, 357 p., 14%-. 

 127 tab. 

 (4) Atwater, W. O., and Rosa, E. B. 



1899. Description of a new respiration calorimeter and experiments on the con- 

 servation of energy in the human body. U. S. Dept. Agr. Office Exp. 

 Sta. Bui. 63, 94 p., 12 fig., 8 pi. 



(5) 



1899. A new respiration calorimeter and experiments on the conservation of 

 energy in the human body. I. /n Phys. Rev., v. 9, no. 3, p. 129-163, 

 12 fig. 

 (6) , Woods, C. D., and Benedict, F. G. 



1897. Report of preliminary investigations on the metabolism of nitrogen and 

 carbon in the human organism, with a respiration calorimeter of 

 special construction. U. S. Dept. Agr. Office Exp. Sta. Bui. 44, 64 p. 

 4 fig- 



