REPORT OF the; preside;nt, 191 i, 25 



be said of them here that they justify expectations and that they increase con- 

 fidence in the capacity of the establishment to advance astrophysical science. 



The Observatory has now, nearly fully equipped and in use, four highly 

 effective telescopes : the Snow, horizontal, 30-inch reflector ; the two tower- 

 telescope refractors; and the 60-inch reflector mounted equatorially. The 

 1 50- foot tower telescope, together with its auxiliary apparatus, constitutes the 

 most important addition of the year in the way of equipment. Varied use of 

 the 60-inch equatorial proves it to be alike effective in visual, photographic, 

 and spectroscopic work. It is especially penetrating in its capacity to reveal 

 the characteristics of globular star clusters and spiral nebulas. 



In view of the repeated failures of the contractors of St. Gobain, France, 

 to cast a perfect disk for the 100-inch "Hooker telescope," it was determined 

 to try the imperfect disk furnished by these contractors, but not accepted, 

 four years ago. Accordingly an agreement was entered into with the makers 

 to try shaping the disk, and to pay therefor in case it proves sufficiently stable 

 after adequate trial. This work was begun early in the year, and good prog- 

 ress has already been made, although some delay must result by reason of the 

 illness of Professor Ritchey and his chief assistant in this delicate and 

 laborious task. In the meantime the glass-founders of St. Gobain are unre- 

 mitting in their efforts to secure a perfect disk. 



It is with deep regret that the Observatory and the Institution are called 

 upon to record the unexpected death, on May 24, 191 1, of Mr. John Daggett 

 Hooker, to whom the enterprise of the 100-inch telescope owes its inception. 

 His intelligent interest in and appreciation of the work of the Mount Wilson 

 Solar Observatory led him to make a gift of $50,000 in 1906 for the pur- 

 chase of a disk and for the shaping of it for a lOO-inch reflecting telescope. 

 Unfortunately the difficulties in the way of casting so large a disk of glass, 

 together with his untimely death, have prevented him from realizing his de- 

 sire to see this telescope in use. But if the enterprise succeeds, as now seems 

 quite hopefully probable, the Observatory and the Institution will be glad to 

 link the constancy of his faith in scientific investigation to the constancy of 

 the stars by means of diligent applications of the "Hooker telescope" to as- 

 tronomical research. 



The magnetic survey of the globe undertaken by this department is pro- 

 ceeding effectively on both land and sea. Observations of the magnetic ele- 

 De rt t f ments of declination, dip, and intensity have been made at 

 Terrestrial numerous poiuts ou the continents of Asia, Africa, Aus- 

 Magnetism. tralia, Europe, South America, and on the Polynesian 

 Islands ; while the non-magnetic ship Carnegie has secured a large quantity 

 of data of immediate practical utility to navigation and of still greater im- 

 portance, doubtless, in their relations to the general problem of terrestrial 

 physics. 



