The Observatory on Mt. Whitney. 145 



favorable condition: i. e., when there was a minimum 

 amount of water vapor in the Earth's atmosphere. Mount 

 Whitney seemed to offer an ideal exposure. Here, if any- 

 where the spectra would be least influenced by the water 

 vapor and oxygen in our own atmosphere. As far back 

 as 1894, when examining the spectrum of Mars at Mount 

 Hamilton for evidence of water vapor, Campbell had 

 realized the need of repeating the work from some level 

 above the water vapor strata. Mount Whitney, altitude 

 4420 meters (14,502 feet) above sea level, in a region of 

 extreme dryness and accessible at the time, appealed to 

 him as the best suited place. Therefore, when the planet 

 was again near the Earth and high above the horizon, he 

 planned to attempt spectroscopic work from the summit 

 of Whitney. Mr. William H. Crocker generously de- 

 frayed the expenses of the party. To make sure of the 

 availability of the site, Campbell and Abbot made a pre- 

 liminary trip in 1908, and remained one night on the sum- 

 mit, August 24th. As a result of their report Dr. Walcott, 

 Secretary of the Smithsonian Institution, authorized the 

 building of a small observatory and shelter from the 

 Hodgkin's fund. May we not hope that this is the 

 nucleus of a great sero-physical observatory where work 

 shall be done that will both add luster to American science 

 and justify in fullest measure the aim of the Smithsonian 

 Institution in its purpose to diffuse knowledge throughout 

 the world for the welfare of men. 



Of the results of the expedition it may be said very 

 briefly that while weather conditions were in the main 

 stormy, there were two excellent nights for the astrono- 

 mers, with an amount of vapor in the air, only a very 

 small fraction of that present during all previous observa- 

 tions. Six excellent spectrograms of Mars and the Moon 

 were obtained, and Dr. Campbell draws the conclusion on 

 this evidence that while there may be water vapor in 

 Mars, it is exceedingly small in amount. It is indeed 

 doubtful if there is much difference between Mars and 

 the Moon, so far as water vapor and oxygen are con- 



