SCIENTIFIC SUMMARY. 
87 
The ratios above give very closely the formula, 2 Si R + Si R 2 , being 
that of two atoms of enstatite or bronzite plus one atom of olivine. The 
mineral is named after Prof. Peckham, to whom the author is indebted for 
every facility in prosecuting his researches in connexion with this remarkable 
meteorite. 
Examination of the Red Felspar of the Granite from Lyme, Conn . — A 
fragment of the beautiful coarse granite from the McCurdy quarry at Lyme, 
Conn., was given by Prof. Blake to M. Des Cloizeaux for optical study. He 
finds it to be a true microcline, but of an altogether peculiar structure, for the 
study of which the ordinary magnifying power is not sufficient, the con- 
stituent parts being exceedingly minute. The face of every cleavage shows a 
series of very small spots of albite, interspersed with hemitropic plates of 
microcline, the angle of extinction of which — not easily determined with 
great exactness — is 13° to 15°, measured from the edge between the two 
cleavage-faces. Across the second cleavage, the structure is, as it were, 
fibrous, and, with a high power, the angle of extinction is found to be from 
7° to 9° for the microcline, and from 18° to 20° for the albite. ( I have never 
before/ he writes, 1 met with a felspar with the elements so crowded together 
and so fine.’ He hopes the proprietor may be able to supply some fragments 
of this beautiful granite. An examination of such specimens would be of 
great interest on account of the enormous size of its felspar individuals.- - 
( Amer . Journ. Sci., 1880, October, xx. 335.) 
PHYSICS. 
Effects of Magnetism on Iron and Steel. — According to some recent 
investigations by Prof. Righi on the effects of magnetism on iron and 
steel, (1) magnetism produces in iron and steel an increase of dimensions in 
direction of the magnetization. (2) On cessation of the magnetizing force a 
part of this increase remains, and more or less of it according to the coercive 
force. (3) The elongations are proportional to the square of the current’s 
intensity when this is not very great. (4) When, after a strong current 
through the spiral, a weak current is sent in the opposite direction, it produces 
a shortening ; but even when it is strong enough to demagnetize the bar, the 
latter retains a greater length than in the normal state. (5) During reversal 
of the polarity of a bar its length becomes momentarily less, and it oscillates 
in length. (6) A bar of wire or iron traversed by a current contracts at the 
moment of closing the circuit. (7) On opening the circuit it elongates, but 
this elongation is less than the initial contraction, indicating that transverse 
magnetism partly remains. (8) In reversal of the transverse polarity the 
bar elongates for a moment, and thus oscillates in length. (9) The contrac- 
tion produced by a current is greater when the bar has before been longitudi- 
nally magnetized. (10) Some iron bars show a tendency to spiral magnetiza- 
tion, i. e., to rotate the magnetic axes of their molecules in the direction of 
the spiral. This, says Nature , is shown by the contractions caused 
by a current passing through the bars, which are different according 
