46 CARNEGIE INSTITUTION 



in South Africa or Argentina are desired, a further small appropria- 

 tion will be necessary. Later, through the operations of Mr. Hussey 

 and the kindness of Sir David Gill, the Committee expects to be 

 in possession of better knowledge as to what may be advisable in 

 this direction. 



BUTLDINGS. 



The question of buildings and other constructions necessary for 

 the proposed observatory is one which cannot be discussed in its 

 minute details until something shall have been determined as to the 

 site. Since the idea of this observatory is that of a temporary 

 observing station, to be occupied, perhaps, not more than ten or 

 twelve years, our ideas of the construction required would be largely 

 controlled by that fact. 



The necessity of providing for the equalization of the inner and 

 outer temperature seems to prescribe for the observing rooms a form 

 of construction which would not be very different whether the ob- 

 servatory were to be temporary or permanent. The essential prin- 

 ciple is that the walls should consist of an iron or steel framework, 

 with an outer covering of wood, in the form of louver work, and 

 an inner covering of sheet metal, such as galvanized iron. The 

 efficiency of this form of construction has been fully tested and 

 seems to leave nothing further to be desired. For the drum to 

 carry a large dome, this form of construction would probably be as 

 economical as any other that could be accepted. Wood might be 

 used for the framework were it not for the necessity of an even and 

 solid construction for the tracks upon which the rolling mechanism 

 of roofs and domes is supported. For the meridian instruments, 

 sliding roofs should be provided. The great superiority of these 

 over the old form of shutters is now fully demonstrated. 



Since an important requirement for site is excellence of atmos- 

 pheric conditions, it follows that the proposed observatory must be 

 located at some distance from any large center of population. 

 Consequently it would be practically unavoidable that provision 

 should be made for housing the observing staff upon the observatory 

 premises. This is an arrangement which is quite indispensable to 

 the highest efficiency in any case. In any but an extremely excep- 

 tional climate there will be a large proportion of nights in which 

 the probability of clear sky during the first half of the night will be 

 doubtful. If observers live within easy access to the instruments, 

 much clear sky will be utilized that will inevitably be lost otherwise. 



