82 



obtained from existing sources, and we are accord- 

 ingly attempting to overcome the peculiar diffi- 

 culties involved in making them. The instrument 

 shop and the underground constant-temperature 

 chamber provided for this purpose are in the 

 Pasadena office-building, where the ruling-machine 

 is now being completed and tested. 



FIG. 58. Grinding Cross Ways of Ruling Machine Bed on Large Planer 



The larger instrument-shop, in an adjoining 

 building, contains a good collection of machine 

 tools of the best types, and the optical shop is 

 equipped for grinding and polishing plane and 

 curved surfaces of various dimensions. Here the 

 loo-inch mirror for a large reflecting telescope is 

 now being figured. 



