66 CARNEGIE INSTITUTION 



Plans and Estimate of Cost. 



As already explained, a principal station and two temporary aux- 

 iliary stations will be needed for the proposed Solar Observ^atory. 

 We recommend that the principal station (A) be established at some 

 such point as Mount Wilson, where Professor Hussey's observations 

 have shown that the conditions are excellent for work on the sun 

 requiring very perfect definition of the image. For the study of the 

 solar constant and the absorption of the earth's atmosphere two 

 auxiliary stations (B and C) will be required for use during the 

 summer months. Station B should occupy a site at the summit of 

 a high mountain, while station C should be near the base of the 

 mountain, some thousands of feet below. In view of the time and 

 expense required. Professor Hussey's study of mountain sites did 

 not include the very high mountains. We have obtained much 

 valuable information regarding conditions on Mount Whitney and 

 other mountains, but a further study of the matter would be required 

 before the sites for stations B and C could be decided upon. While 

 Mount Wilson would probably serve the purposes of the principal 

 station, there should nevertheless be a further and more prolonged 

 study of sites for this purpose, to be made while the equipment is 

 under construction. Recent experience indicates a probability that 

 stations B and C might be discontinued after observations have been 

 made at these points for two or three seasons, since it is probable 

 that all the work of the observatory could then be done at such a 

 point as Mount Wilson. 



Principal Station (A). 



The summit of Mount Wilson is about 8 miles in an air line from 

 Pasadena. At present it is reached from the base of the mountain 

 by either one of two trails, suitable for pack animals, but not adapted 

 for wagons. One of the first considerations, therefore, would be the 

 problem of providing adequate transportation facilities. This might 

 be done (i) by constructing a wagon road from the foot of the 

 mountain to the top ; (2) by constructing an electric railway from 

 Pasadena to the summit of the mountain ; (3) by extending to 

 Mount Wilson the electric railway that now terminates on Mount 

 Lowe. Owners of the property on the summit of Mount Wilson 

 state very positively their conviction that one of the two latter 

 projects would be carried out in case this site were selected. This 

 would naturally be an important consideration in the final decision 



