608 



SCIENCE. 



[N. S. Vol. XVII. No. 433. 



subjects, and must undertake occasional 

 theoretical studies, as well as computations 

 of considerable extent. 



The hydraulic engine for turning the 

 dome of the great telescope had been work- 

 ing badly for several years, limiting to 

 an appreciable extent the productiveness 

 of the telescope itself. It was found that 

 the brass feed-cylinders of the engine 

 were badly worn, permitting very consid- 

 erable leakage, thereby in effect decreas- 

 ing the hydraulic pressure on the pistons. 

 The cylinders were drilled true, and new 

 piston-heads were provided. It is grat- 

 ifying to report that the dome and its en- 

 tire mechanism now perform at least as 

 satisfactorily as they did when new. 



The original design of the great tele- 

 scope did not provide for power to wind 

 the driving clock; it was wound by hand. 

 A Pelton water-wheel was installed for 

 this purpose in 1890, but it never had 

 sufficient power to do the work without 

 assistance from the observer. In the past 

 year the water power has been applied 

 more directly to the wheel. The winding 

 apparatus now acts immediately, without 

 assistance from the observer. 



Further to increase its efficiency, Mr. 

 Wright has designed, and the instrument- 

 maker has constructed, a device for turn- 

 ing the water power on and off automat- 

 ically. This will be put in place in the 

 near future; and it is hoped that the ob- 

 server's duties in connection with the clock 

 will be confined to starting it in the even- 

 ing and stopping it in the morning. 



The need of a wind screen in the open- 

 ing of the dome had been felt for many 

 years. The violent vibration of the tele- 

 scope when the opening was turned toward 

 the wind made it impossible to secure accu- 

 rate observations. An effective screen was 

 erected in 1901. 



The efficiency of the thirty-six-inch 

 equatorial was enormously increased a few 



years ago by illuminating the setting cir- 

 cles by means of electric lights operated 

 from the eye end, thereby making it unnec- 

 essary for the observer to climb the high 

 mounting, as he had theretofore done 

 many times per night. Astronomer Hus- 

 sey has recently equipped the twelve-inch 

 equatorial (under his charge) in a similar 

 manner, with good results. 



Many minor improvements on the 

 mounting of the Crossley Reflector have 

 contributed somewhat to its stability, but 

 the necessity for providing this instru- 

 ment with a new mounting has become 

 more apparent with time to all who have 

 used it. Director Keeler's remarkable 

 success was achieved at enormous expense 

 of time and physical energy. On the 

 average, it was necessary for him to make 

 four or five exposures on an object before 

 a suitable negative was secured; and in 

 many cases he had to be satisfied with en- 

 larged and elongated star images. His 

 experiences have been those of Assistant 

 Astronomer Perrine, who is now in charge 

 of the instrument. If the mirror were 

 provided with a suitable mounting, ob- 

 servers possessing their great skill should 

 have no difficulty in obtaining three suc- 

 cessful negatives out of four attempts. 

 The regents in 1901 authorized the con- 

 struction of a new mounting,^ and it is 

 well under way. 



A generation ago the astronomer ordered 

 his telescope, and expected it to meet 

 all his requirements. This is no longer 

 sufficient. The wonderful developments of 

 our science call for special instruments to 

 do special work, and the so-called univer- 

 sal instrument is out of date. This is es- 

 pecially true in investigations along astro- 

 physical lines. The successful instrument 

 must have maximum efficiency in the prob- 

 lem to be solved. Every observatory of 

 our class requires an instrument-making 

 shop near at hand. This requirement is 



