206 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1953 



formulate the laws from which Newton deduced the general laws of 

 motion. 



Today the time at which the stars pass an indicating point in a 

 fixed telescope is observed in order to check our computation of time, 

 and studies have been made even recently of minute differences in 

 the observed and calculated movement of the planets. Observations 

 of the movements of the stars themselves are still being continued, but 

 all this is now a small portion of astronomical work, which is con- 

 cerned primarily with the study of the probable composition of the 

 stars and of their life history, their probable origin, and their eventual 

 fate. The popular picture of an astronomer is perhaps still that of 

 an oldish man looking through a large telescope and noting down the 

 readings that he makes of the positions of the stars. Many years ago, 

 however, such recordings by the astronomer were replaced by a young 

 lady measuring a photographic plate under a micrometer, for today 

 all the observing is recorded by photography, and the really pains- 

 taking work is done by the computer, who measures the plates and 

 reduces the observations to tables. A telescope today is a camera, 

 and for all scientific purposes the eye has been replaced by the photo- 

 graphic plate. 



Over 40 years ago, when I was still in England, I had a visit from 

 F. H. Seares, the assistant, as he was then, to G. E. Hale at Mount 

 Wilson Observatory. Dr. Seares told me of the importance to the 

 astronomer of the quality of the photographic plates he used and 

 said that Dr. Hale believed that the most important advance that 

 could be made in astronomical practice was to increase the effective 

 sensitivity of the plates available. He asked if I would be willing 

 to come to Mount Wilson and try to make improved plates for 

 astronomical work. I told him that I had just accepted Mr. East- 

 man's invitation to go to Kochester to found a research laboratory for 

 the Eastman Kodak Co. and that I hoped that in my work at Rochester 

 I might be able to develop improved photographic materials for 

 astronomical use. This promise was not forgotten, and I kept in 

 touch with the people at Mount Wilson after we started work at 

 Rochester. 



What astronomers want in general are plates that will take photo- 

 graphs in less time; that is, plates that are more sensitive to light. 

 Unfortunately, however, those plates must have properties that are 

 not easy to combine with increased speed. The astronomers want 

 all the speed that can be obtained; they want the sharpest possible 

 image ; and they want the least possible graininess. 



At first it might appear that the demand of astronomers for more 

 sensitive plates does not differ from the requirements of other 

 photographers. As the years have passed, the sensitivity of photo- 

 graphic materials has been increased, but everybody still wants more 



