446 
rorULAR SCIENCE REVIEW. 
Ice Machine for Brewers. — MM. L. Martin and Vindliaussen have 
given lengthy and full descriptions of two apparatus based upon the principle 
that, if the expansion of a gas (atmospheric air in this instance) is effected by 
mechanical means, absorption of heat — in other words, production of cold — 
takes place. The ice-making machine produces 100 kilos, of ice at a cost 
of about sixpence. The cooling apparatus is so arranged as to effect a 
drying of the malt and cool the wort at the same time. — Revue hebdoma - 
daire de Chimie. 
The Emission of Heat. — Herr G. Magnus continues his observations on 
this point. The last instalment of this lengthy memoir is divided into the 
following sections : — On reflection of heat ; description of experiments ; re- 
flection from the surface of other substances than silver, glass, rock-salt, and 
sylvine ; reflection under various angles; results. — Ann., der Physik , No. 4. 
Galvanic Element with one Liquid. — A description of such an apparatus is 
given in the Revue hebdomadaire de Chimie (July 14). It is a galvanic cell 
composed of zinc and carbon placed in a fluid made up of 40 parts of water, 
4-o parts of bichromate of potassa, 9 parts of concentrated sulphuric acid, 
4 parts of sulphate of soda, and 4 parts of the double sulphate of potassa 
and iron. This element produces a very regular current. The zinc need 
not be amalgamated, and no gas is evolved. 
A Strai (jht-needled Galvanometer. — A description, illustrated by woodcuts, 
appears in the Revue hebdomadaire de Chimie by M. Bourbouze. The object 
of the inventor is to render slight deviations visible to a large number of 
students simultaneously. 
Underr/round Temperature. — From observations that have been carried on 
from 18G4 to 1870 by MM. A. 0. Becquerel and E. Becquerel, it seems that 
at 36 metres below the surface the temperature is constantly 12*47°, and 
that at a depth of from 36 to 26 metres a very slight difference only is 
observed. The paper contains a lengthened series of tabulated results. — 
Comptes-rendus , July 18. 
Contribution to Terrestrial Magnetism. — We learn from the Proceedings of 
the Royal Society that a valuable paper on the above has been sent in by 
General Sir Edward Sabine, K.C.B., the President. It is accompanied by 
maps of the declination, inclination, and magnetic force, which have been 
drawn at the Hydrographic Office of the Admiralty under the superinten- 
dence of Captain Frederick John Evans, R.N., F.lt.S. The paper consists 
in great measure of Tables, giving the observation of each of the three mag- 
netic elements, with reductions in every cose for the secular change between 
the date of the observation and that of the epoch (1842-5) for which the 
maps are constructed. 
ZOOLOGY AND COMPARATIVE ANATOMY. 
Eyes in the Mole . — The mole is blind. Not so the foetal mole, which Mr. 
R. I. Lee, in a pnper read before the Royal Society (April 28), proves: Mr. 
I ee's paper is not very fully published in the Proceedings; but such as it 
i**, it contains much information. It concludes as follows : — It must neces- 
sarily happen that many interesting observations are made in the course of 
