Obituary Notices. 
547 
Assistant Secretary, and soon afterwards Secretary, to the 
Smithsonian Institution. This connection continued uninter- 
ruptedly until his death on the 27th of February this year. The 
variety of his successful employments bears eloquent wutness to 
the magnitude of his mental equipment : engineer, architect, 
mathematician, physicist, astronomer, and administrator by 
profession, he was also a successful writer, a student of art and 
of archaeology. 
The great characteristic of Langley’s work is its pioneer nature. 
Problems of like type to problems already solved had no attraction 
for him. New problems which presented no special difficulty in 
their solution were passed by. The problem whose difficulties 
were such that others had failed to solve it, the problem whose 
difficulties were such that no other had attempted to attack it — 
these were the problems which Langley attacked and mastered ; 
and his attack was conducted almost with impatience. He never 
sat down beforehand to perfect a method of procedure ; he began 
at once on what he believed to be the likeliest' lines, and perfected 
his method as he proceeded. 
A subject which had once attracted Langley attracted him 
always. Questions arising in his earliest work appeared again in 
work which was uncompleted at the time of his death. All his 
investigations arose naturally, as all great investigations do, in 
the course of daily labour. It would serve no useful purpose to 
enumerate them here. It seems better that a mere indication of 
their nature and extent should be given, along with a fresh 
expression of this Society’s appreciation thereof. 
Between the years 1870 and 1877 Langley’s attention was 
devoted to the question of the structure of the solar disc and 
the radiation of heat from its various portions. The results were 
published in a series of papers during that period. It is found 
that, the more perfect are the atmospheric conditions for observa- 
tion, the more closely do present-day results agree with Langley’s 
early drawings. The practical aim of all his work is well in- 
dicated by a paper, in that series, on the direct effect of sun-spots 
on terrestrial climates. 
Another, and perhaps the most distinctive, branch of his work 
was that which dealt with the distribution of energy in the solar 
