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Chemistry and Physics. 401 
centre and between the two lines H in the violet, an ill defined dark space. 
When fluorescent paper was made to receive the spectrum, this dark 
ace became at once sharply defined. The er upon 
chinin-paper than upon the other fluorescent substances which the author 
d, and he confined himself to this in his investigation. The author gives 
a mathematical investigation of the spectrum as produced by parallel open- 
ings, and then makes with the compasses upon the fluorescent paper the 
Tequisite measurements of the distances of the points where the first 
bright spectrum of the diffracted light commences. The wave length is 
then given by the formula 4—=e sin y, in which e represents the distance 
between two successive lattice-openings and y the angle which the dif- 
ted ray makes with the normal to the surface of the lattice. By 
Placing a violet-colored glass over the opening near the heliostat, the 
most refrangible end of the spectrum became visible with still greater 
distinctness and exhibited the sharpest termination: even on common 
measurements the following wave lengths in fractions of a millimeter. 
Extreme visible red rays = 00007064 
Extreme visible violet rays 4 == 0°0003956. 
Most refrangible invisible rays 4 = 00003540. ee 
Hence it appears that light from the extreme red to the extreme invisible 
ray embraces a complete octave. 
With the view of confirming this result. the author produced upon 
e object-glass and a Munich 
nees of these lines were measured B, and | as 
ordinates upon an axis of abscissas upon which the single distances of 
ordinates are expressed by the difference of the corresponding wave 
lengths, In this manner the author obtained a curve which from the line 
H to the extreme invisible ray appears to follow the same law as the other 
Portions of the spectrum. Fisenlohr has furthermore found that crown 
does nog absorb the invisible rays in such a manner as to shorten 
reing a hole in the screen 
the invisible rays fell the 
SECOND SERIES, VOL. XXII, NO. 66,—NOV-, 1856. 
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