335 
EXPEEIMENTAL ILLUSTEATIONS OF THE MODES 
OF DETEEMININO THE COMPOSITION OF THE 
SUN AND OTHEE HEAVENLY BODIES BY THE 
SPECTEUM. 
A Lectuee delivered to the Working Mex of Exeter, August 21, 
1869. By WM. ALLEN MILLEE, M.D., D.C.L., V.P.R.S. 
[PLATE L.] 
O NE of the most important features of the age in wliich we 
live is the rapid manner in which man’s knowledge of the 
powers and properties of the different substances around him is 
being extended. We behold, on all sides, an extraordinary 
growth of what is called physical science^ and we witness every- 
where the increasing command which this increased knowledge 
gives to man over the materials of which this globe consists. 
I shall devote the time which we are to spend together this 
evening to an illustration of some of the modes in which this 
mastery of mind over matter is to be obtained ; and in this review 
shall draw my examples mainly from the striking achievements 
recently performed in the application of optics to chemistry, 
usually described under the term of spectrum analysis. 
Marvellous as are many of the revelations of science, it is to 
be noted that the methods of their discovery may generally be 
resolved into the application of ordinary observation to the 
objects to be examined. The distinction between ordinary and 
scientific observation is, indeed, merely in the degree of its 
accuracy. The man of science is perpetually contriving means 
to render his observations strictly accurate, and to reduce them, 
whenever it is practicable, to a form in which their results may 
be represented by weight or by measure. 
To take a simple instance : There is, perhaps, no great diffi- 
culty, even to those unfamiliar with science, in believing that 
sound is produced by the vibratory motions of the sounding 
body transmitted through the air to the ear ; since when a harp- 
string is suddenly stretched, or the cord of a piano is struck, a 
tremulous motion of the string is seen to accompany the sound 
thus produced ; and as the motion • becomes less visible the 
sound gradually dies away. It is not difficult to render these 
VOL. VIII. — KO. XXXIII. Z 
