84 REPORTS ON INVESTIGATIONS AND PROJECTS. 



reflector are being made with the 24-inch grinding machine. The plane 

 mirrors must be given an elliptical form, and a special machine for grind- 

 ing their edges in this form has been designed and constructed. 



Other w^ork of the optical shop has included the completion of a mirror 

 of 24 inches aperture and 143 feet focal length for the Snow telescope, 

 and a 20-inch plane mirror for testing purposes. Small plane mirrors for 

 the heliomicrometer, and concave mirrors for use in the laboratory, have 

 also been made. 



Except for the delay occasioned by the San Francisco earthquake, the 

 progress of the work on the mounting for the 60-inch reflector has been 

 very satisfactory. An erecting house, 70 by 20 feet, and 25 feet high, 

 was constructed in the spring on our grounds in Pasadena. In this was 

 installed an electric traveling crane, capable of carrying loads of 15 tons. 

 This crane has proved most efficient in operation, permitting the heavy 

 parts of the mounting to be handled with the greatest ease. 



The mounting, as constructed by the Union Iron Works Company, and 

 delivered at our shop early in September, comprises the following parts : 



Triangular base, 15 feet long and 9 feet wide at the widest part. This is divided 



longitudinally into two parts, each of them weighing 3^/2 tons. 

 Upper bearing, or column, for polar axis, weighing about 4^4 tons. 

 Lower bearing for polar axis. 



Hollow nickel steel polar axis, 15 feet long, weighing 4J/2 tons. 

 Hollow steel float, 10 feet in diameter, weighing 4 tons. 

 Mercury trough, bolted to upper bearing and carrying the mercury in which the moving 



parts of the telescope are floated. 

 Cast-iron fork, weighing 5 tons, to be bolted to upper end of polar axis. 

 Worm-gear, 10 feet in diameter, weighing nearly 2 tons. The teeth of this worm-gear 



will be cut by our own machinists. 

 Bevel-gear, 7J4 feet in diameter, weighing 1%. tons, fitting with the worm-gear on the 



polar axis, and connected with electric motor for quick motion in right ascension. 



The skeleton steel tube of the telescope is not yet completed by the 

 Union Iron Works Company. The work on the instrument to be done 

 in our own shop comprises the cutting of the worm-gear ; the construction 

 and fitting of the driving-clock (now nearly completed) ; the attachment 

 of electric motors for quick and slow motions; the construction of a 

 support system for the 60-inch mirror; supports for the small mirrors, 

 etc. The entire instrument will be completed and tested by actual obser- 

 vations in Pasadena before it is taken to Mount Wilson. 



The electric truck, on which the parts of the mounting are to be carried 

 over the Mount Wilson road, is nearing completion at the shops of the 

 Couple-Gear Freight-Wheel Company in Grand Rapids, Michigan. This 

 truck, which was specially designed for the present work, will be capable 

 of carrying loads of 5 tons. It is fitted with steering gear at both ends, 

 and in other respects is adapted for the difficult work of transportation 

 over a steep and narrow road. 



