ASTRONOMY — HALE. 7 I 



BUILDINGS AND EQUIPMENT ON MOUNT WILSON. 



Ill the present report it is unnecessary to refer at length to the 

 design and construction of buildings, as the}" will be fully described 

 in other publications. For the sake of completeness, however, a 

 brief account will be given of the work of construction hitherto 

 accomplished. 



Temporary Building for 15-inch Ccelostat Telescope. — This inexpen- 

 sive structure was erected in the spring of 1904 and served admirably 

 for the experiments with the small ccelostat and 6-inch objective of 

 60-foot focal length brought out from the Yerkes Observatory. This 

 work was of special value in determining the design of the rjermanent 

 building for the Snow telescope. 



The " Casino." — An old log cabin, used many years ago for the 

 entertainment of visitors at Strain's Camp, now belonging to the Pas- 

 adena and Mount WilsonToll-road Company, was made habitable and 

 occupied until December, 1904, by the members of the staff on Mount 

 Wilson. It was also used during all last season and a part of this 

 for the workmen's mess. 



Snow Telescope Building. — This building has been described in 

 Contributions from the Solar Observatory No. 2. It was completed 

 in the summer of 1905, including ail electric wiring, plumbing for 

 dark-rooms, fire protection, etc. The framework is of steel and the 

 canvas covering, chosen because it heats but little in the sun, is 

 painted with fireproof paint, found by our tests to be very effective. 

 As stated elsewhere in this report, the louvres and roof ventilation of 

 this building have answered their purpose admirably. 



Mount Wilson Shop and Power-house. — This building, described 

 in No. 2 of the "Contributions," contains the gasoline engine, 

 dynamo, and switchboard of the electric plant, as well as the tools 

 needed for work of construction and repair on the mountain. The 

 storage battery of thirty cells, installed here temporarily, has now 

 been placed, with a second battery of sixty cells, in a separate build- 

 ing. The operation of the engine, using distillate in place of gaso- 

 line, has shown that electric power can be generated at very low cost 

 on Mount Wilson, in spite of the heavy expense of " packing " the 

 distillate to the summit. Thepower plant, though originally designed 

 for the purpose of the expedition for solar research, may possibly 

 serve, with some additions, for the much heavier demands of the 

 Solar Observatory. 



Storage- Battery House. — The intense heat experienced for a period 

 of several days last summer and the limited space available in the 

 small power-house led me to design an underground building of 



