506 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 52 



keep it from jolts, while I leaned over the back seasick, and all at 

 3.30 a. m., September 9. 



"Yours truly, C. G. Abbot. 



"Mr. C. D. Walcott, 



"Secretary Smithsonian Institution." 



The observations of Director Campbell on the spectrum of Mars 

 were entirely conclusive in showing that water-vapor, if present at 

 all in the atmosphere of Mars, is in less quantity than is contained in 

 the extremely rare and dry part of the earth's atmosphere which is 

 above Mount Whitney. In fact, no evidence at all of water-vapor 

 on Mars was detected by Campbell. 



The writer's experiments involved the use of a cornplete spectro- 

 bolometric outfit in the determination of the solar constant of radia- 

 tion, and it was the first occasion in which this complex apparatus 

 had ever been used at so great an elevation. Fortunately it worked 

 well, the observations were highly satisfactory, and they yielded 

 results which confirm almost exactly the accuracy of the work done 

 by Smithsonian observers at Mounts Wilson and Washington in 

 recent years. Unfortunately both Director Campbell and myself 

 were on Mount Whitney during unusually unfavorable weather, for 

 the whole Southwest, including northern Mexico, was just at that 

 time visited by floods of rain and cloudy weather. Such a condition 

 would not probably be met with at that season one year in ten. 



It is the hope of the Smithsonian Institution that many observing 

 expeditions in many branches of science will apply in the years to 

 come for the use of its shelter on Mount Whitney. There are few 

 mountain peaks in the world of like elevation which are so readily 

 accessible, or which present more nearly the conditions of dryness 

 and marvelous transparency of air which would be expected in high 

 flights with balloons. Persons who desire to work upon ATount 

 Whitney should apply to the Secretary of the Smithsonian Institu- 

 tion for information or permission to use the house there. 



