MOUNT WILSON SOLAR OBSERVATORY. 233 



the engines during the very severe service on the mountain grades. 

 The exceptionally powerful engine and frame of the larger truck are 

 supplemented with a special gear-train to permit the transportation 

 of loads as great as 5 tons in case of necessity, at a low rate of speed. 

 Both trucks have been in regular service since their purchase, and 

 have made daily round trips from Pasadena to the mountain, with 

 but very few exceptions. The rapid transportation of material in 

 this way has made it possible to complete the large pier and the 

 foundations for the 100-inch- telescope mounting and building within 

 a single season. Moreover, it is greatly to the advantage of the 

 members of the staff, who formerly walked or rode up the old trail, 

 to be able to leave Pasadena any morning at Q^'SO"' and reach the 

 summit of Mount Wilson before noon. 



The substitution of heavy motor trucks running daily for lighter 

 mule teams going up on alternate days involves increased wear of the 

 mountain road, which now demands more constant care. Addi- 

 tional daily labor will make it possible to continue the use of the road, 

 almost without interruption, through the winter season, when it was 

 formerly closed for several months. It will also reduce materially 

 the heavy spring task of removing from the road the slides of earth 

 brought down by winter rains. 



CONSTRUCTION WORK IN PASADENA. 



The trucks are housed in a garage built at the rear of the land, 

 across the front of which stands the office-building. It is accordingly 

 in a convenient position relative to the main shop-building and the 

 storehouse at which most of the material for transportation is 

 assembled. The garage contains space for four large trucks and is 

 built of sheet iron, with a concrete floor. It has two repair pits and 

 a tool and oil room, and is equipped with an underground gasoline 

 storage system with a Bowser pump. The space between the garage 

 and the rear of the office-building will be kept available for such 

 portions of the telescope mounting as may require storage or erection 

 in Pasadena previous to the,ir transportation to Mount Wilson. 



The requirement for larger shop-tools necessitated by the con- 

 struction of many parts of the 100-inch telescope mounting and the 

 auxiliary instruments to be used with it demanded an increase in the 

 shop floor-space. Since the completion of the office building had 

 made available a considerable amount of space in the Hooker build- 

 ing previously used for offices, the simple plan was adopted of trans- 

 ferring all of the optical work to this building and utilizing the room 

 made in this way for th'^ additional shop machinery. This plan 

 has the obvious advantage of bringing all of the optical work into 

 one building and of separating it completely from the machine- 

 shop. A number of the partitions which separated the optical rooms 

 have been removed, thus adding about 70 per cent to the original 



