78 



REPORT OF THE SECRETARY. 



The greater number of working days have been devoted to the production of a 

 large number of holographs of the upper infra-red spectrum made under widely 

 varying conditions for the purpose of studying the possible causes of the errors 

 which have been roughly indicated above. To this end an investigation of the per- 

 sonalities of different observers, as they may affect the final results of each observa- 

 tion, has also been undertaken. 



B. The classification, detailed examination, and final reduction of holographs to 

 the linear translations, or " cylindrics," which resemble in appearance photographs 

 of the visible spectrum, has kept pace with the production of the most satisfactory 

 curves. 



The production of these linear spectra involves the services of a photographer 

 during three to five days in each instance, and extreme accuracy; for this reason, 

 only the best of the curves obtained are subjected to this process. The table given 

 below includes only those plates which are free from defects, and consequently rep- 

 resents but a small part of the labor involved in the production of results which 

 may seem intrinsically small : 



II. 



Lineai' translations made {plates 10 X SO cm.). 



Bolographs of infra-red spectrum from- 



a to par 



par to £2 



fito4."5... 



"Hox 



Total 



Number of 



cylindrici= 



made. 



Cylindric 

 negatives. 



Composites. 



8 ! 5 



8 ' 2 



4 







6 



4 



26 



11 



The following table shows the number of plates developed : 



III. 

 Whole number of plates developed. 





1894. 



1895. 





July. 



Aug. 



Sept. 



Oct. 



16 



20 

 5 



Nov. 



Dec. 



Jan. 



Feb. Mar. 



Apr. 



May. 



June. 



For linear translations . . . 



42 



5 



31 



8 

 

 



20 



12 







21 

 9 

 3 



5 



35 

 10 



3 



21 

 



8 



24 







11 



10 

 38 





 43 

 11 



7 



45 







9 

 13 



Other photographs 



2 



C. The development of the instruments used, to as near mechanical perfection as 

 it is possible to obtain with the means at command and under the conditions pre- 

 vailing in the observatory, has constituted, for the reasons given above, a very 

 large part of the work up to the present time. 



The siderostat has been furnished with a new counterpoise for the altazimuth 

 mirror support, a new direction axis and base for the mirror, and a new polar axis, 

 resting upon ball bearings, completed December 1, 1894. This massive instrument, 

 which has been greatly modified since it left the maker's hands until it has taken 

 the form shown in the annexed illustration, is now capable of being brought to 

 exact adjustment, and needs only the addition of a new governor for its driving 

 clock to make it most efficient. 



With the hope of compensating in some degree for the extreme variations of tern-, 

 perature due to the construction of the present building, a conduit for warm air in 

 winter and cold air in summer from the blowers iu the Smithsonian building was 

 constructed. The coils of piping for bringing the admitted air to the proper tem- 

 perature after it has reached the observatory are not yet complete, and the need of 



