268 Scientific Intelligence. 
former case the polarization has often appeared perfect, or all but 
It is possible that this may in some measure have been 
due to the circumstance, that when a given quantity of light is 
iminished in a given ratio, the illumination is perceived with more 
difficulty when the light is diffused uniformly, than when it is 
spread over the same space, but collected into specks. Be this as 
it may, there was at least no tendency observed toward polariza- 
tion in a plane perpendicular to the plane of reflection, when the 
suspended particles became finer, and therefore the beam more 
nearly continuous.” 
Through the courtesy of its owner, I have been permitted to see 
and to experiment with the piece of plate glass above referred to. 
Placed in front of the electric lamp, whether edgeways or trans- 
versely, it discharges bluish polarized light laterally, the color 
i no means a bad imitation of the blue of the sky. 
Prof. Stokes considers that this deportment may be invoked to 
decide the question of the direction of the vibrations of polarized 
light. On this point I would say, if it can be demonstrated that 
excess of alcohol. 
The selenite rings constitute an extremely delicate test as to. the 
pope of motes in a liquid. Commencing with distilled water, 
or example, a thickish beam of light is necessary to make the 
larization of its motes sensible. A much thinner beam suffices for 
common water; while with Briicke’s precipitated mastic, a beam 
too thin to produce any sensible effect with most other liquids, suf 
fices to bring out vividly the selenite colors—Proc. Roy. Soe, 
XV, 223, Jan., 1869, gee 
2. Note on the Formation and Phenomena of Clouds ; hs J io 
ordin- 
Tynpatz.—lIt is well known tk 
ary undried air is exha a 
f th r 
few strokes of the pump. It is, as might be expected, possible to 
produce clouds in this way with ths celts of other liquids than 
water. : 
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