ABSTRACTS 



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RADIATION. — The emissivity of straight and helical filaments of 

 tungsten. W. W. Coblentz. Bureau of Standards Scientific 

 Paper No. 300 (Bull. Bur. Stds., 14: 115-131). 1917. 

 In the present investigation the radiation both from the inside and 

 from the outside of the turn of a helically wound tungsten filament in 

 an atmosphere of nitrogen was studied. It was found that the intensity 

 of the radiation from within the turn of the helix is from 90 to 100 per 

 cent greater than from a similar area on the outside of the turn. This 

 is accounted for on the basis of multiple reflection within the helix. 

 This reflection modifies the quality of the light so that it is redder than 

 the light from the outside of the turn. The close agreement between 

 the observed infra-red measurements of the radiation from within 

 the helix and the computed values (obtained on the basis of multiple 

 reflection and the reflectivity of tungsten) confirms the belief that the 

 phenomenon is the result of multiple reflection. Tests made with a 

 nicol prism, showed that the fight from within the filament is highly 

 polarized. This and the infra-red energy measurements both indicate 

 that the quality of the radiation emitted differs from that of a black 

 body. There is no indication that the temperature within the helix 

 is higher than on the outside of the turn. A difference in temperature 

 of 200° would be required to account for the observed difference in 

 brightness. W. W. C. 



CALORIMETRY. — An aneroid calorimeter for specific and latent heats. 



Nathan S. Osborne. Bureau of Standards Scientific Paper No. 



301 (Bull. Bur. Stds., 14: 133-157). 1917. 



The principle of the unstirred or "aneroid" type of calorimeter 



has been embodied in an instrument especially designed for deter- 



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