522 PROCEEDINGS OF THE AMERICAN ACADEMY 



" In reply to your inquiry ' as to the present status of researches 

 now in progress which have received aid from the Rumford Fund/ I 

 would state that three remarkably fine prisms have already been pur- 

 chased, and the other optical parts have been ordered, for the new 

 spectrograph designed for the determination of stellar velocities in the 

 line of sight, in aid of which research a grant of $500 was made last 

 autumn. 



" It is hoped that the spectrograph may be completed and the regu- 

 lar work with the instrument may be begun during the present summer, 

 and I shall therefore expect to be able to announce some results of the 

 investigations for your next annual meeting." 



PROFESSOR GEORGE E. HALE. 



Grant of November 10, 1897, $400, for the purpose of completing 

 a spectroheliograph. 



"The spectroheliograph was first attached to the 40-inch telescope 

 last December. Preliminary tests in the laboratory had shown it to be 

 extremely satisfactory from an optical point of view, at least in so far 

 as the definition and contrast of the photographs of spectra were con- 

 cerned. As we were without a skilled instrument maker at the obser- 

 vatory for several montlis last summer and autumn, I had the moving 

 plate holder and second slit constructed by au instrument maker in 

 Chicago. The first tests with the telescope showed the presence of a 

 mechanical defect, which caused the plates to be striped with lines a 

 millimeter apart, the pitch of the screw which drives the plate-carriage. 

 A series of experiments showed that these lines were due in large part, 

 if not altogether, to the absence of suitable end-thrust bearings for the 

 screw, and to the poor construction of the screw, nut, plate-carriage, etc. 

 It was then decided to completely reconstruct this part of the spectro- 

 heliograph in our own shop. End-thrust bearings were supplied, together 

 with a new screw, which was carefully ground. As the result of the 

 work the millimeter lines did not appear on the photographs taken 

 after the change had been made. It was found, however, that the 

 plate was still covered with fine lines about one quarter of a milli- 

 meter apart. These are shown on the plate which I will send you in 

 a few days. In order to remove these lines a large number of experi- 

 ments were required, but at last, plates practically free from lines, and 

 even smoother than those obtained with the very satisfactory hydraulic 

 apparatus of the Kenwood spectroheliograph, were secured. Tiie diffi- 



