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OF THE SOLAR SPECTRUM. 539 
the minimum of deviation of the luminous ray: he then saw an 
infinite number of vertical stripes or lines of different thicknesses. 
These lines are darker than the rest of the spectrum; some 
amongst them even appear quite black. The distances of these 
‘lines, or their relative positions, do not undergo any change, 
neither by that of the aperture of the shutter, nor by the removal 
of the telescope from this aperture. Neither the nature of the 
_ substance of the prism nor its refractive angle prevent these lines 
from being distinguished ; they only become stronger or weaker ; 
but the ratios of their respective distances seem to be the same 
for all refractive substances. 
_ Fig. 1, which has been made from the drawing of Fraunhofer, 
and which is a quarter its size, represents the luminous spectrum 
“with all its lines. The red nearly terminates at A, the violet, 
or the limit which follows the violet, at I; we cannot speak with 
Bron: respecting these limits, which are more distinct at the 
ed than at the violet. 
If the light of an illuminated cloud fall on the prism through 
e same aperture, the spectrum appears to be limited on one 
3 between G and H, on the other at B: the direct light of 
the sun therefore aapeds the spectrum nearly the half of its 
length. 
_ At A there is a well-marked line; the red, however, continues 
little further; at @ is a mass of fine lines. The line B is of a 
ther considerable tint and thickness. From B to C there are 
nine well-determined lines. C is thick and black like B.  Be- 
_ tween C and D there are thirty fine lines, which, if two of them 
_ are excepted, can only be perceived by being strongly magnified, 
4 with prisms of great dimensions. D is formed by two strong 
‘lines separated by a bright line. Between D and E we meet 
with about eighty-four lines of different size. E consists of 
_ several lines, of which the middle one is the strongest: from 
_ Eto B there are about twenty-four lines. 6 is formed of three 
} Baines, two of which are separated by a fine and bright line; 
_6F contains fifty-two stripes. F is very large; between F and 
G there are 185 stripes of different dimensions; at G are 
| erowded together many lines, several of which are remarkable 
| for their size; from G to H we reckon 190 stripes; the two 
bands H are nearly equal, and formed of several lines, in the 
midst of which there is one very strong one; from H to I they 
are in very great numbers. 
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