CELESTIAL SPECTROSCOPY.* 
By WILLIAM HUGGINS, F. R. 8. 
In 1866, I had the honor of bringing before this Association, at one of 
the evening lectures, an account of the first fruits of the novel and un- 
expected advances in our knowledge of the celestial bodies which fol- 
lowed rapidly upon Kirchhoff’s original work on the solar spectrum 
and the interpretation of its lines. 
Since that time a great harvest has been gathered in the same field 
by many reapers. Spectroscopic astronomy has become a distinct and 
acknowledged branch of the science, possessing a large literature of 
its own, and observatories specially devoted toit. The more recent dis- 
covery of the gelatine dry plate has given a further greatimpetus to this 
modern side of astronomy and has opened a pathway into the unknown 
of which even an enthusiast thirty years ago would scarcely have dared 
to dream. 
In no science, perhaps, does the sober statement of the results which 
have been achieved appeal so strongly to the imagination and make 
so evident the almost boundless powers of the mind of man. By 
means of its light alone to analyze the chemical nature of a far-distant 
body; to be able to reason about its present state in relation to the 
past and future; to measure within an English mile or less per second 
the otherwise invisible motion which it may have towards or from us; 
to do more, to make even that which is darkness to our eyes light, and 
from vibrations which our organs of sight are powerless to perceive 
to evolve a revelation in which we see mirrored some of the stages 
through which the stars may pass in their slow evolutional progress— 
surely the record of such achievements, however poor the form of 
words in which they may be described, is worthy to be regarded as the 
scientific epic of the present century. 
Spectroscopic methods.—I do not purpose to attempt a survey of the 
progress of spectroscopic astronomy from its birth at Heidelberg in 1859, 
but to point out what we do know at present, as distinguished from what 
“*Presidential address to the British Association for the Advancement of Science, 
tat Cardiff, August, 1891. (Report of Brit. Assoc, 1891, vol. LXI, pp. 3-37.) 
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