280 CARNEGIE INSTITUTION OF WASHINGTON. 



Miss Wolfe served as librarian until November 1. Since then she 

 has devoted her time exclusively to the reduction and discussion of 

 results relating to the work of stellar photometry, the sun's general 

 magnetic field, and the fields associated with sun-spots. 



On November 1 Miss Haines resumed her position as librarian and 

 in addition has given assistance in the compilation and tabulation of 

 results relating to the work of the division. She has also aided in the 

 editorial work and in the preparation of manuscripts, proof-reading, etc. 



The library has been increased by 545 bound volumes during the 

 year — 271 by purchase, 205 by binding, and 69 by gift. The total 

 number of volumes is now 3,676. 



The Observatory is much indebted to Mrs. Katharine Hooker for a 

 large portrait, in oils, of the late Mr. John D. Hooker, and to Mrs. 

 Henry Draper for a portrait of the late Dr. John S. Billings and several 

 original negatives by Dr. Henry Draper. 



CONSTRUCTION DIVISION. 

 WORK OF THE INSTRUMENT SHOP. 



The ruling-machine has advanced to the point where visible progress 

 is slow, on account of the extreme delicacy of the various operations 

 involved. Mr. Jacomini spent several weeks with Dr. Anderson at 

 the Johns Hopkins University in the autumn, familiarizing himself 

 with the various adjustments and tests of the Rowland- Anderson ruling- 

 machine, and experimenting with certain alloys which promise to afford 

 good material for grating plates. He also spent a week at the Fore 

 River Ship Company's yards at Quincy, Massachusetts, inspecting the 

 work in progress on the 100-inch reflector mounting. On his return 

 to Pasadena he devoted himself to the long and tedious task of grinding 

 and straightening the ways. The machine was inclosed in a house of 

 wood and glass, which materially improves the temperature control. 

 Tests with a Callendar recorder showed a maximum temperature range 

 of about 0?01 C. in the course of a month, with much smaller daily 

 fluctuations. The hydraulic driving system was perfected, with most 

 satisfactory results, through the improvement of a commercial water- 

 motor of 0.1 horse-power, which now gives ample power with a head 

 of only about 33 feet. The experiments on various forms of end-thrust 

 bearings led to the adoption of a ruby-steel combination, which leaves 

 nothing to be desired. A reconstructed ruby about half an inch in 

 diameter was given a plane figure by Mr. Jacomini, and mounted in 

 conjunction with a highly polished convex surface of hardened steel. 

 Optical tests show that a high degree of precision has been attained 

 in figuring and centering these bearings. The machine is now nearly 

 readj^ for the exhaustive cross-ruling tests devised by Dr. Anderson, 



In addition to the work on the mounting of the 100-inch telescope, 

 which occupied about half the time of the instrument shop, the large 



