a 
r 
60 J. C. F. Ziliner on a new Spectroscope. 
ferent appearance; for example, they are blurred on the edge 
nd of different breadth, as is precisely the case with the line F 
in the spectrum of Sirius. 
e most essential of these difficulties, which have hitherto 
ARS a definite solution of the problem in question, I believe 
that I have successfully overcome, by a new construction of the 
spectroscope, the first example of which I have the honor to 
exhibit here to the Royal Society. 
The arrangement is in essentials the following. The line of 
light produced by a slit, or a cylindrical lens, lies in the focus of 
a lens which as in all spectroscopes renders parallel the rays to be 
‘dispersed. Then the rays pass through two Amici’s direct-vis- _ 
ion prism-systems of excellent quality, which J obtained from 
the optical establishment of Merz in Munich. 
"hese are fastened to one another in such a manner that 
though each passes one half of the pencil of rays proceeding 
from the collimator object-glass, and also so that the refracting 
angles lie on opposite sides. In this way the collected pencil 
of rays will be dispersed in the two spectra in an opposite di-— 
rection. The object-glass of the observing telescope, which 
unites the rays again to an image, is perpendicular to the re- 
fracting angles of the prisms placed horizontally, and as in the 
heliometer, is divided; each of the two halves can be moved 
micrometrically both parallel to the line of section and perpen-. 
icular to it. By means of this we can bring the lines of one 
ous into coincidence with those of the other, and also place 
the s i i 
