that he might live to explore through a telescope of this mag- 

 nitude, the realms far beyond what we now call outer space. 

 Enthused by this thought, he entered into communication with 

 the Carnegie Institution at Washington, and offered to give the 

 sum of Fifty thousand Dollars for the manufacture of a Re- 

 flector of this size. The proposition was accepted and there 

 was no delay in prosecuting the work. The order for the cast- 

 ing of the glass disk was given in September. 1906, to the 

 French Plate Glass Companies at St. Gobain. France, ami dur- 

 ing the year between the Spring of 1907 and June, 1908, six 

 or eight castings were made. 



In order that there might be no delay in grinding polish- 

 ing and figuring the disk after its arrival. Mr. Hooker con- 

 structed at Pasadena, in the Winter of 1907. a building which 

 he supplied with all necessary appliances. The main room is 

 34 feet square and 20 feet high, and opens into a long testing- 

 hall. 



'The walls of this room are very heavy, made of brick 

 laid in cement, and covered with a roof of reinforced concrete. 

 This portion of the building, which is separated from the 

 other part by iron doors, may therefore be regarded as tire 

 and earthquake proof — a consideration of no small importance, 

 in view of the nature of the work to be done within it. A 

 heavy si eel I-beam, supported over the doorway, carries a 

 traveling crane, by means of which the mirror-disk and heavy 

 parts of the grinding-maehine. one of which weighs 3.5 tons, 

 can be brought into the room and handled when necessary 

 during the progress of the work. The testing-hall, 100 feet 

 long and 10 feet wide, will permit the mirror to be tested from 

 the center of curvature or with parallel light. . . . On 

 one side of the testing-hall are rooms for the grinding and 

 polishing tools and for the apparatus required to maintain the 

 polishing room at a uniform temperature. There is also a 

 large fireproof vault, for the storage of astronomical photo- 

 graphs. On the other side of the hall a series of computing 

 offices is provided, affording, with the rooms already available 

 in the adjoining building, suitable accommodations for a large 

 staff of computers."* 



In June, 1908, information was received at Los Angeles 

 from the Glass Companies at St. Gobain that the casting of a 

 perfect disk 102 inches in diameter. 131/4 inches thick and 

 weighing -i 1 /^ tons, had been successfully accomplished. On 

 December second. 1908, in its iron ease, it reached the end of 

 its long journey and it was deposited in the Hooker building 

 at Pasadena, but upon being unpacked it was immediately seen 



* Annual Report. 1907. of Prof. George E. Hale. Director of the Mount 

 Wilson Solar Observatory of the Carnegie Institution of Washington. 



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