264 
POPULAR SCIE'NCE REVIEW. 
dispensers of medicine. The lip of a bottle is sensibly anniiloid. The 
amount of solid in contact with the dropping liquid is determined by the 
size of two diameters, one measuring the thickness of the rim of the neck, 
the other the width of that run itself. 
(5.) The drop-size depends upon the chemical nature of the solid from 
which the drop falls, and little or nothing upon its density. Of all the solids 
examined, antimony delivers the smallest and tin the largest drops. 
(6.) The drop-size depends upon temperature. Generally, the higher the 
temperature the smaller the drop. With water the effect of a change of 
temperature of 20° to 30° centigrade is very small. 
(7.) The nature or tension of the gaseous medium has little or no effect 
upon the drop-size. 
The Flovj of Solid Bodies submitted to great Pressure. — 1\I. Tresca lately 
communicated a very interesting paper under the above title to the French 
Academy. The writer’s conclusions are particularly interesting, as bearing 
upon the celebrated theory of the cause of the motion of glaciers, which was 
put forward some years since by Forbes. The hjq)othesis to which we refer 
was based upon the supposition that in glaciers the particles of ice are not 
so fir ml y united together as is generally believed, but have the power of flowing 
over each other. On this view Forbes regarded the motion of an icy sea not as 
simply the sliding of the entire mass through a valley, but as the movement 
of a great mass of particles, which have not only travelled over the land 
beneath, but over each other also ; in fact, that a glacier was a very slow- 
flowing river, in which, as in a stream of water, the particles in the centre 
flowed more rapidly than those lying next the bank. It seemed hard to 
conceive that a substance, whose particles possess such an intense cohesive 
power as those of ice, could be capable of flowing in the manner indicated ; 
but the researches of M. Tresca show that even in metals the same phe- 
nomena appear. The result of numerous experiments proved to him that, 
without undergoing any alteration of state, solid bodies flow from an orifice 
in exactly the same manner as liquids when sufiicient pressure is applied to 
them. The soft metals were those principally experimented on, and from ■ 
repeated observations, M. Tresca concludes that there is a imity of con- 
stitution in all matter, and that masses of the most solid metals are formed 
of separate and mobile — Vide Comptes Bendus, LIX., No. 19, 
p. 754. 
The Spectra of some of the Nebulce. — The most startling announcement 
which has been made by science for some years is that which is contamed 
in the results of Messrs. Huggins and Miller’s examination of the lighr 
of the nebulae. In a former paper these gentlemen demonstrated by 
spectral analysis the similarity of constitution between our sun and the 
fixed stars. In the last communication they stated the results of their 
examination of the nebulae, and their arrival at a very different con- 
clusion from that stated in their former paper. The first nebula was in 
Draco, 37 H. iv. The light of this nebula, unlike that of any other ex-ter- 
restrial body hitherto examined, was not composed of light of different re- 
frangibility, and hence was incapable of forming a spectrum. A gneater part 
was monochromatic, and after passing through the prisms remaiaed concen- 
trated in a bright light which occupied in the instrument the portion of that 
