COBLENTZ: MODIFICATIONS OF THERMOPILES 511 



There are cases in which it may be convenient to determine a 

 him.]) correction for both ratio and phase angle instead of determ- 

 ining and correcting for them separately, for example, the case 

 of a watthom* meter and a cm-rent transformer metering the 

 power supplied to an inductive load. This may even be extended 

 to the case of the combination of a current and a voltage trans- 

 former. 



Portable watthour meters are more convenient than the house 

 type with graduated disks as the trouble of counting is eliminated. 

 In testing current" transformers a five-ampere range is more eco- 

 nomical of time than a ten-ampere range. One-ampere or two- 

 ampere ranges should not be used with current transformers as 

 the impedance introduced into the secondary is too great. 



It is important that the constants of the standard transformer 

 should have been tested under actual working conditions of 

 load, including the meter. 



The acciu-acy of the method is ample for commercial require- 

 ments, the results are independent of ordinary line fluctuations, 

 and no special apparatus is required. 



PHYSIC^. ^ — Various modifications of thermopiles having a con- 

 tinuous absorbing surface.^ W. W. Coblentz, Bureau of 

 Standards. 



In a previous paper (Bull. Bur. Standards No. 188) an account 

 was given of the construction and the behavior of thermopiles 

 composed of bismuth and silver wires with rectangular absorb- 

 ing sm-faces of tin attached to the junctures of these two metals. 

 The novelty of the design consists in a series of overlapping 

 receivers, forming a continuous surface which has all the ad- 

 vantages of a good bolometer, with none of its disadvantages. 

 The present paper deals with the construction and the behavior 

 of various modifications of this type of thermoelement, adapted 

 to various problems in biology, physiology, psychology, physics, 

 and astronomy. 



It was found that,, by joining the thermoelements^ — ^two in 

 series — parallel, the heat capacity of the corriposite receiver was 



1 Detailed paper to appear in the Bureau of Standards Bulletin. 



