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POPULAR SCIENCE REVIEW. 
which formed its periphery, and a screw, the figures could be brought into 
view successively, the movement being a spiral one, inasmuch as there 
was no fixed axis, — a spring in front keeping the disk in situ . Nothing 
could exceed the beauty of the various images produced in this instrument 
by the diffraction of the light as it traversed the minute figures. We 
learn that this enterprising firm is about to introduce a new polariscope 
also, by which even the angular difficulties presented by crystals of 
sulphate of copper will be overcome. 
Machine for ascertaining Ocean Depths. — M. Gouezel has invented a new 
form of this apparatus. The great objection to the variety now employed 
is, that currents in the water cause the line of suspension to be bent, and 
so the apparent depth, judged of by the length of line employed, is much 
greater than the real depth. The purpose to which the new “ sounder ” 
is intended to be applied is for the construction of a chart of the bottom 
of the ocean, which would be of service in the laying of telegraph cables ; 
and apart from such uses, the possession of such a map would be of great 
scientific interest. In M. Goiiezel’s apparatus the suspension line is 
altogether dispensed with ; a rod of iron, furnished with nippers at its 
extremity, supports a cylindrical weight capable of being detached from 
the rod, and above the weight is fixed a float of hollow metal. On striking 
the bottom of the water the weight is detached and the remainder floats 
to the surface ; a small clock, inclosed in the apparatus, is so arranged 
as to close at the moment of concussion, so that the time of descent can be 
estimated ; a bell is also attached ; an easily visible object is placed above 
the whole, so that there is no difficulty in finding the apparatus after its 
arrival at the surface. 
Analysis of Solar Light. — There are few researches of more interest than 
those of M. Janssen, referring to the modifications presented by the solar 
spectrum according to the different hours of the day. This savan has 
discovered that the obscure bands which present themselves under certain 
circumstances may be resolved into numerous and very distinct rays. 
Moreover, these rays are perceptible, not only during the morning and 
evening, when the sun is near the horizon, but even — though less clearly — 
at midday, when the sun is at its highest point. Finally, these same rays 
have been observed in light from both the moon and stars, hence they cannot 
result from any peculiar influence of our atmosphere. This disco s T ery 
was achieved with a small spectroscope with direct vision, somewhat like 
Amici’s, but with modifications in adaptation to the objects held in view. — 
Vide Comptes Rendus , May 2, 1864. 
Advantages of Fixed Conductors. — M.Volpicelli, who has given great con- 
sideration to the relative examination of various forms of electric conduc- 
tors, has been at last impressed with the conviction that the fixed variety 
is the most useful and effective. The following are some of the reasons 
which he gives in support of his choice : — 
1st. It cannot be logically denied that the fixed conductor, combined 
with the condenser, has the power of manifesting atmospheric 
electricity very well. 
2nd. M. Peltier has demonstrated, by a series of experiments, that 
