28 REPORT OF THE SECRETARY. 



park features by greater care of the indigenous trees and the phmting 

 of copses where such are required, by the establishment of seats, and 

 by perfecting the roads and walks as far as practicable. The park is 

 now the nearest to the city of any large stretch of open, picturesque 

 country, and this would seem to be almost a duty owed to the public. 



This again brings to mind a project often urged upon Congress, but 

 never realized b}' an actual appropriation for the work. I refer to 

 the plan for extending the park to the nearest boundary road on the 

 southeast and the west. This has often been referred to in previous 

 annual reports, and it would seem that the present time is particularly 

 favorable for the accomplishment of this object, since roads have 

 recently been established by act of Congress quite near to the present 

 boundaries. 



Among the more pressing needs of the park is a small building 

 with outlying yards, which can be used as a hospital and quarantine 

 for sick animals and, incidentally, as a ^pathological and anatomical 

 laboratory. In this connection, in view of the fact that the primary 

 object of the park is for " the advancement of science," it must be 

 considered hoAv much our knowledge has been increased by such es- 

 tablishments as the Jardin des Plantes, of Paris, under Buflfon, Cuvier, 

 or Milne-Edwards ; the gardens of the Zoological Society in London, 

 by Huxley and others, and those at Berlin and elsewhere. I approve 

 the recommendation of the superintendent that a modest laboratory 

 for pathological research be added to the park equipment. 



During the last year the number of visitors to the park has further 

 increased, and it is not too much to say that no equal expenditure by 

 Congress has brought so much of instruction and rational enjoyment 

 to the people. 



ASTROPHYSICAL OBSERVATOEY. 



As for several years past, the operations of the Astrophj^sical 

 Observatory have been almost wholly directed toward measuring the 

 amount of the solar radiation, and its loss in transmission through 

 the sun's envelope and through our own atmosphere. 



I do not yet regard the evidence of solar variability as conclusive, 

 but still as rendering this conclusion more probable, and I am glad 

 to state that two lines of investigation have this year become very 

 prominent in the work of the Observatory, which will almost cer- 

 tainly lead to a conclusion regarding this important question. 



The first of these is the almost daily bolometric examination of the 

 large solar image formed by the great horizontal telescope, for the 

 purpose of detecting changes in the transparency of the solar absorb- 

 ing envelope. This work depends so little on the transparency^ of our 



