MOUNT WILSON OBSERVATORY. 255 



possible to do so, that is, to about 0.000005 inch. Some minor changes were 

 also made in the bearings for the screw, in order to obviate any tendency 

 toward unequal wear of the pivots. 



The investigation of the small residual errors in the spacing-wheel is nearing 

 completion. 



BUILDINGS, GENERAL CONSTRUCTION, AND TRANSPORTATION. 



Construction work on Mount Wilson, under the superintendence of Mr. 

 G. D. Jones, has included a large concrete water-storage reservoir with a 

 capacity of 530,000 gallons, the laying of 1,700 feet of concrete conduit, the 

 addition of a steel roof to the Monastery, and the construction of a temporary 

 laboratory and piers for Professor Michelson's experiments. General repairs 

 have been carried on as usual. Nearly all the Observatory buildings in 

 Pasadena have been repainted during the year. 



Mr. Dowd, engineer on Mount Wilson, and Mr. Sidney Jones, assistant 

 engineer, have rewired the 60-inch telescope, laid the electrical cables in the 

 new conduit line, and made numerous additions to the electrical equipment 

 of the 100-inch telescope and other instruments. 



The mountain road suffered comparatively little damage from the remark- 

 ably severe storms of the past winter, and transportation was carried on with 

 but little interruption, except at times of heavy snowfall. A 1^-ton White 

 motor truck has been purchased for use on the road and has been equipped 

 for both passenger and freight service. 



