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POPULAR SCIENCE REVIEW. 
made the first of the drawings described above. In these negatives the 
equatorial belt is almost absolutely transparent. As Mr. Browning remarks, 
(l the light from the orange-coloured belt has failed entirely to act on the 
sensitive collodion surface.” In negatives taken during previous years, the 
equatorial belt has exerted the most marked action on the collodion film, so 
that the belt has come out quite opaque. 
Browning 1 s Automatic Spectroscope . — The principle of this ingenious 
instrument has been made the object of several rival claims, which seem to 
us to have no foundation whatever. On the one hand, Herr von Littrow 
claims for his son (lately deceased) the invention of the plan, and in con- 
firmation of the claim points to a volume of the Proceedings of the 
Imperial Society of Vienna. On reference to this volume we find an auto- 
matic spectroscope described, which bears not the most remote resemblance 
to Mr. Browning’s, and would certainly not reward the mechanician who 
should attempt to remove it from the domain of pictures. On the other 
hand, Professor Young, in describing an instrument he has successfully 
employed himself, speaks of Mr. Rutherford as the originator of the idea 
of slotted bars working over a central pin. He mentions no date, however, 
nor does he give any evidence whatever to show that Mr. Browning had 
had the opportunity of hearing of Mr. Rutherford’s ideas. Now Mr. 
Browning can prove that, so far back as 1862, the idea of his automatic 
spectroscope had not only been conceived by him, but described to others. 
As the automatic spectroscope is a most important addition to our spectro- 
scopic appliances, it does seem desirable that those who advocate the claims 
of others to its invention should give satisfactory evidence in support of 
their views. But it may be remarked, in passing, that the mere enunciation 
of the idea that slotted bars attached to the prisms would give the required 
motion would by no means suffice to establish a claim as against Mr. Browning. 
A modification of the plan first described by Mr. Browning has been 
suggested by Mr. Proctor, and at the last meeting of the Royal Astrono- 
mical Society Mr. Browning exhibited a spectroscope constructed on this 
modified plan. It presents certain improvements. The theoretical require- 
ments of an automatic spectroscope to give minimum deviation for all rays are 
strictly fulfilled, and, further, the motion of the viewing-telescope is guided by 
the same slot-movement which controls the motion of the several prisms. 
It is proper to point out, however, that these improvements must be regarded 
as essentially included within Mr. Browning’s own plan. Mr. Proctor 
claims no share of the credit due to the modified instrument: and this is but 
simple justice, since surely nothing can be more unfair than to step in 
between an inventor and those improvements which are sure to follow the 
first construction of a new instrument, and then to claim the improved 
instrument as one’s own. 
Double and Twice-acting Automatic Spectroscope . — Mr. Proctor has pro- 
posed a plan, which we believe Mr. Browning is carrying out, for extending 
the automatic principle to a second battery of prisms, an intermediate 
prism of four faces carrying the light from one battery to the other. Of 
this prism three faces act on the light. At the first there is refraction, at 
the next total reflection, and at the third refraction again. As at each re- 
fraction the dispersion is increased precisely as when the light passes into or 
