74 REPORTS ON INVESTIGATIONS AND PROJECTS. 



The '■ Monastery ." — The offices and living quarters provided for 

 the members of the staff in this building (described in Contribution 

 No. 2) have proved very satisfactory. The librarj' and current 

 journals are also kept here. All the members of the staff, with the 

 members of the visiting expeditions, meet regularly at meals in the 

 common dining-room. The opportunity thus afforded for the in- 

 formal discussion of scientific questions is one of the most attractive 

 features of life at the observatory. 



Guest- House . — The need of suitable accommodations for visiting 

 men of science has been recognized by Mr. John D. Hooker, to whom 

 we were already indebted for meeting the expenses of the Hooker 

 Expedition. The guest-house, recently erected and furnished at 

 Mr. Hooker's expense, contains two bed-rooms and a large living 

 room, with broad piazzas extending the entire length of the building 

 on the east and west sides. It has alreadj^ proved of the greatest 

 service in the entertainment of guests, thus serving as an important 

 adjunct of the " Monastery." 



General Laboratory . — The prompt and accurate interpretation of 

 the results of astrophysical research is a matter of the first impor- 

 tance in planning the work of an observatory. On the one hand, if 

 the observations, as in the present case, are made for the most part 

 by photographic means, the problem of providing suitable devices 

 for the measurement and reduction of the plates presents itself. 

 In some instances the measures must be of the highest possible 

 precision, while in others simple devices for measurement or com- 

 putation may save a great amount of time and expense without in 

 any wise detracting from the value of the results. Special attention 

 has been devoted to these considerations. But it is not enough to 

 accumulate a vast series of measures without undertaking such ex- 

 periments as may be required for their interpretation. Accordingly, 

 a laboratory has been built on Mount Wilson for the measure- 

 ment and reduction of the photographs and the comparative study 

 of the radiations emitted by various substances under widely different 

 conditions of temperature, pressure, strength of surrounding mag- 

 netic field, etc. In order to provide against the destruction by fire of 

 the collection of photographs, the building is constructed of cement 

 blocks, with cement floor and partitions, metal ceiling, and metal- 

 sheathed roof. It is 27 by 70 feet in size, and thus of sufficient 

 length to contain the special globe apparatus for measuring solar 

 photographs, already referred to in this report. Other measuring 

 machines have also been mentioned in the discussion of the solar 

 investigations. The chief apparatus in the spectroscopic laboratory 



