SCIENTIFIC SUMMARY. 
557 
through a small achromatic telescope, with a magnifying power of between 
five and six diameters. Angular measures of the different parts of the 
spectrum were obtained by means of a micrometric screw, by which the 
position of the small telescope was regulated. A reflecting prism was 
placed over one half of the slit of the spectroscope, and by means of a 
mirror suitably adjusted, the spectra of comparison were viewed simulta- 
neously with the stellar spectra. — Vide Chemical News , June 11th. 
Action of Heat on Minerals. — Dr. Phipson draws two conclusions from 
his experiments on this subject. (1) That mineral bodies can absorb a 
certain amount of heat (not indicated by the thermometer), which becomes 
latent, and this is effected without the bodies undergoing any change of 
state. (2) That they slowly part with this heat again, until they have 
acquired their original densities which had been diminished. (3) This 
property having been found to be possessed by very many substances, it 
will probably be observed, ere long, in all bodies without exception. — Vide 
a paper read before the Royal Society, May 26, 1864. 
Hicks ’ Standard Barometer . — This instrument, which was described to 
one of our scientific societies as an entirely new instrument, is apparently 
an invention of ancient date. In a letter to the editor of the Chemical 
News (May 28), Mr. W. Symons alleges that the apparatus in question has 
been described, in principle, in the seventh edition of the “ Encyclopaedia 
Britannica,” which appeared in 1842, and remarks that the circumstance 
does not reflect credit upon those connected with the institution to which 
he refers. 
New Electro-magnetic Induction Machine . — Mr. J. B. Thompson has 
invented a machine of this kind, the proposed objects being (1) To obtain 
by means of magnetic induction, from a few voltaic pairs, a continuous 
stream of electricity in one direction, and of any required tension. (2) 
The induced stream of electricity to be as manageable as that from the small 
exciting battery. (3) The machine to be entirely self-acting. These ends 
have been attained : 1st, By associating two or more induction coils in such 
a manner that when the magnetism in one coil or set of coils ceases, it 
shall be excited in the other, the resulting induced alternate current or 
sets of currents being caused to flow in one and the same direction. 2nd, 
These induced currents are brought under control by means of a four-port 
reversing commutator, whose diagonal parts are connected so that by simple 
oscillation its contacts are reversed, just before the reversal of the cur- 
rents. 3rd, The small exciting battery used in this machine not only 
excites the electro-magnets in the coils, but at the same time drives a 
rotatory break and oscillating commutator. By means of these several 
contrivances the machine becomes a perfectly self-acting one. The size of 
the battery being diminished, as also the consumption of material and the 
labour, it must effect a considerable pecuniary saving, and on this account 
commends itself to the notice of physicists. — Vide Electrician , May, 1864. 
Improved Form of Telegraph Insulator. — At a recent meeting of the 
Franklin Institute, Mr. Thayer exhibited his new form of insulator. The 
body is composed of a block of glass protected by a well-shaped casing of 
cast-iron, through an opening in the top of which the glass projects, the 
casing being strongly cemented to the glass. To that portion of the glass 
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