the transportation of many hundreds of tons of 

 materials, the erection of brick, steel, and concrete 

 structures, the execution of an observational pro- 

 gram, the measurement and reduction of thou- 

 sands of photographs, and the imitation of celes- 

 tial phenomena by laboratory experiments, have 

 taxed the capacity of a large staff of workers. The 

 equipment is now so nearly complete and the plan 

 of investigation so definitely outlined that a brief 

 description of some typical methods and results 

 may be of service to the visitor and to the general 

 reader interested in the progress of astrophysical 

 research. 



OLD METHODS AND NEW. 



An observatory, like any other laboratory of 

 research, may concentrate its attention upon either 

 one of two widely different objects: the accumu- 

 lation of great stores of data in existing depart- 

 ments of knowledge, or the opening up and explo- 

 ration of new fields of investigation. In both cases 

 extensive series of routine observations are re- 

 quired, but the point of view and the mode of 

 attack are essentially different. In known fields, 

 long since efficiently occupied, standard methods 

 of observation and instruments obtainable from 

 skilled makers are available for use. With the aid 

 of such instruments and methods, perhaps modi- 

 fied and perfected in various details, observations 

 of great precision and importance can be obtained. 

 Moreover, by the preparation of a suitable scheme, 

 well exemplified in Kapteyn's work on the struc- 



