438 ASTROPHYSICS 



larger endowments acutely, the need was almost anticipated by a 

 stream of benefaction. If this stream had its chief source in the 

 United States, its beneficial effects have poured over the whole world; 

 and induced currents have begun to flow elsewhere. We may reflect 

 with thankfulness how much harder our advance might have been 

 but for the noble gifts to the Harvard, the Lick, and the Yerkes ob- 

 servatories: and earnestly hope that the cheerful expectations of 

 a great American astronomer, that these are but the foreshadowing 

 of much larger gifts to science, may be adequately realized. 



May I now turn to one or two of the problems with which this 

 new development of our work has brought us face to face? They are 

 numerous and serious, and it is impossible to consider many of them, 

 perhaps even the most important of them. One of the most press- 

 ing is the problem of rendering generally accessible the vast accumu- 

 lations of material for study that have been suddenly thrust upon 

 our attention. How are our photographs to be stored, preserved, and 

 published? Even now troubles have gathered, and time will only 

 multiply them. It is many years since Professor Pickering drew 

 attention to the difficulties in storing the photographic plates taken 

 at the Harvard Observatory; when many thousands of photographs 

 have been accumulated, not only the space they occupy, but the 

 actual weight of glass, is an embarrassment. And there seems to be no 

 doubt concerning the duty of accumulation. May I confess an early 

 and mistaken view which I formulated on this matter? I reasoned 

 thus: The proper moment for making use of a photograph taken last 

 night is to-day. It is useless to defer the examination until to-morrow, 

 for there will then be new photographs claiming attention. Hence, 

 it is unscientific to take more photographs than can be dealt with 

 immediately. This seemed to be a plausible argument and to show 

 a way out of the difficulty, for if a photograph had once been ade- 

 quately examined, it need not be stored so carefully, and there would 

 not in any case be many to store. But Professor Pickering has demon- 

 strated many times over that the view is untenable. By taking photo- 

 graphs almost recklessly, and without any hope of dealing with even 

 a fraction of them, he has created the possibility of tracing the history 

 of celestial events backwards. When new objects are discovered 

 he can go to his shelves and tell us how long they were visible previous 

 to discovery: and this information is so valuable that we must cer- 

 tainly arrange our future plans with reference to it. It is quite certain 

 that we must be prepared to deal with enormous accumulations of 

 plates, to store them in proper order, and to catalogue them; and 

 if it has already been found difficult to do this for the collection of 

 a single observatory during twenty years, what can we look for in the 

 centuries to come? 



