544 E. BECQUEREL ON THE CONSTITUTION 
for a long time to the action of the spectrum, there is an action 
which is manifested from F as far as the extreme red; this effect 
arises only, as I have already said, from the action of the con- 
tinuing rays, which act upon the impressed substance by means 
of the diffused light which accompanies the solar spectrum. 
This action may be obtained in a higher degree by impressing 
the whole plate at first. 
If we draw the lines and measure accurately their respective 
distances, we find that between H and A there are the same 
lines as in the case of the luminous rays and identically at the 
same distances; but in the chemical spectrum we only see the 
great and moderate lines. It is impossible to produce the finest 
lines by projection, for the spectrum thus obtained is never so 
distinct as when seen through a telescope, and the reason of this 
is obvious, for the focus of the lens changes for each ray. We 
see, however, according to the drawing represented in fig. 3, 
which I have endeavoured to render as faithful as possible, that 
it is certain that the same lines exist in the luminous spectrum 
and in the chemical spectrum, and that the same cause which 
has determined the production of the lines in the solar spectrum 
has also determined those of the chemical spectrum. 
Beyond H the chemical spectrum has an infinite number of 
lines. About as far as M they are still the same as those of the 
luminous spectrum; but further on the luminous rays always 
become feeble; they are no longer comparable: it is probable, 
however, that, if these last extended beyond, we should find the 
same lines as those of the spectrum which we are about to 
describe. 
At first, after the two lines H, we see a great number of lines, 
and among these a very broad line I, formed by the union of a 
great number of smaller lines. After it, at M, come four lines 
remarkable for their distinctness; they are of the same size and 
nearly equally distant ; the last only is a little further off. These 
four lines occur towards the limit Y of the last gray-violet lumi- 
nous rays. Beyond these lines, at N, are four other lines stronger 
than the preceding, nearly equal to each other, the fourth being 
rather broader than the others. There are at O two great lines 
at the same distance from each other as the two lines H, the 
first being a little stronger than the second; then come other 
strong lines, amongst which we distinguish the line P, which is _ 
very strong and very black ; after the latter there are others, but 
