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SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76 



not permit of the actual program of ozone measurements being started 

 this year, so that it is postponed for another season. 



By the kind assistance of Dr. E. F. Nichols, of the Nela Research 

 Laboratories in Cleveland, and his colleague, Dr. Tear, a radiometer, 

 an instrument similar in principle to the blackened vanes which 

 revolve in the glass bulb in the optician's show window, was employed 

 for the measurements of the heat of the spectra of ten of the brighter 

 stars. It proved possible to measure them very easily and very accur- 



^ 40' 20' 1° 40' <?0' D ^0' 40' r ^0' 40' 2° 20' 40' 3 



Fig. 30. — Observed Prismatic Energy Spectrum Curves of tlie Sun and Stars. 



ately with this instrument. Indications observed were all abotit the 

 same magnitude as those which were obtained last year with the 

 bolometer, but owing to the great simplicity and consequent steadi- 

 ness of the radiometer, the accuracy obtained this \ear was very much 

 superior to that which was attained last year. The results secured 

 were of very high interest to all astronomers who have seen them. It 

 looks as if this method of studying the stars would prove of much 

 value. 



It is possible, in this way, by comparison with the sun, to determine 

 the intensity of star heat nearly as accurately as we can determine the 



