﻿NO. lO SMITHSONIAN EXPLORATIONS, I923 27 



investigations were proposed: i. Further study of the use of the 

 sun's heat for cooking purposes, first reported in the Exploration 

 Pamphlet of 1920; 2, the study of the effects of ozone in the earth's 

 atmosphere ; 3, a repetition, with improved apparatus, of the measure- 

 ments of the heat of the spectra of the brighter stars, first attempted 

 in 1922, in the focus of the 100-inch telescope of the Carnegie Obser- 

 vatory on Mt. Wilson. 



Some progress was made with the solar cooker, and oven tempera- 

 tures up to 175° C. were reached. At this high temperature, the oil 

 circulating system sprung leaks and soaked the insulating material 

 which, thereby becoming combustible, spontaneously took fire. So the 

 experiments had to be discontinued. It is proposed to rebuild the solar 

 cooking apparatus for further experiments another year. 



The measurements of ozone in the atmosphere have very interesting 

 aspects. The French observers, Fabry and Buisson, have worked out 

 photographic methods of determining the quantities of ozone. This 

 gas, formed by the action of ultra-violet sun rays upon oxygen, occurs 

 very high up in the atmosphere and is scarcely found in appreciable 

 quantities at the earth's surface. The measurements of Fabry and 

 Buisson indicate that the quantity existing in the higher atmosphere, 

 although small, is sufficient to produce notable absorption, indeed ex- 

 tinction, of the extreme ultra-violet sun rays, and the quantity seems 

 to vary from day to day through a range of even as much as 20 per 

 cent. These variations in the atmospheric ozone would not be of im- 

 portance meteorologically if the effects were restricted to the ultra- 

 violet regions. For the quantity of solar rays there is small and, 

 besides, the extinction of them 1>y the ozone is always so complete that 

 variations are insignificant. However, in the far distant infra-red 

 spectrum region there is a strong absorption band of ozone exactly 

 where the earth itself sends out rays to space. Those are rays which, 

 cooling the earth, maintain the balance of temperature dependent on 

 the equality of the rays which the earth sends out and those which it 

 receives from the sun. 



By comparison of the results of Fabry and Buisson with variations 

 of the sun reported from our stations, it seems likely that there is a 

 dependence of the quantity of atmospheric ozone on the intensity of 

 the sun's heat. If so, we have here an indirect influence on the earth's 

 temperature, depending upon the variations of this infra-red ozone 

 band, for it falls precisely in the only region of the infra-red where 

 otherwise the atmosphere is transparent to the earth's rays. Apparatus 

 w^as set up at IMt. Wilson for the study of this question, but time did 



