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POPULAR SCIENCE REVIEW. 
ments it appears that these cavities in the grains of powder are due to the 
gases developed at the moment of ignition, which burst in various directions 
under very high pressure. This fact has been demonstrated experimentally 
by the mode in which the gases of gunpowder, under a pressure of almost a 
thousand atmospheres, act upon spheroids of zinc submitted to them. In 
the same way, when meteorites enter our atmosphere with the enormous 
velocity of 20 to 30 kilometres per second, they are subjected to very great 
pressure, producing energetic gyratory movements. Whirling in this way 
under great pressure the air tends to act like a screw-tap, and this mechanical 
action is in general accompanied and reinforced by the chemical action due to 
the combustible nature of the meteoritic rocks at high temperatures. — Bull . 
Soc. Geol. de France , February, 1877. 
Parhelion at Campan. — One of those phenomena which, in more super- 
stitious ages, would have set all that witnessed it in a state of alarm, was 
observed by M. Soucaze at Campan, in France, on February 5 last. The 
sun, at one o’clock was surrounded by an immense luminous circle, occu- 
pying about 50 degrees. At the rising and setting of the sun, when 
it was at about the same height above the horizon, this circle contained two 
exactly similar luminous points, each about three times the apparent 
volume of the sun, and exhibiting a sort of tail like that of a comet on the 
side opposite to the sun. The light of the circle was white and faint ; the 
two mock suns displayed all the colours of the rainbow, which extended also 
over the whole of the tails. — Comptes rendus , March 5, 1877. 
Great American Meteor . — On the evening of Thursday, 21st December, 
1876, according to a notice in u Silliman’s Journal,” February, 1877, 
a meteor of unusual size and brilliancy passed over the States of Kansas, 
Missouri, Illinois, Indiana, and Ohio. Professor Newton regards it as 
worthy of special record in many respects, and gives the best account of it 
that he could compile from newspaper reports and letters. The meteor 
appears to have been first seen over the State of Kansas, probably as far west 
as the centre of the State. It passed nearly over, and probably south of the 
cities of Topeka and Leavenworth, when it was at an altitude of about sixty 
miles. Over the centre of the State of Missouri one or more explosions 
occurred ; and shortly after crossing the Mississippi, which it did between 
Hannibal and Keokuk, but nearer to the former place, the meteor broke 
into several fragments. This breaking up continued while it was crossing 
the States of Illinois, Indiana, and Ohio. A loud explosion occurred as far 
east as Concord and Erie; in fact, according to Professor Newton, the 
meteor consisted of a large flock of brilliant balls chasing each other across 
the sky, the number being variously estimated at from 20 to 100. This 
flight is of peculiar interest, on account of the long continued violent disin- 
tegration. The region round Chicago was overcast, and though the clouds 
were remarkably illuminated, the meteor itself was not seen, nor were any 
sounds heard there. From St. Louis no sound is reported. But over all the cen- 
tre of Illinois, between those two cities, a terrific series of explosions occurred. 
The sound was also heard at Keokuk, in Iowa, but apparently not elsewhere 
in that State. Over the northern part of Indiana the passage of the meteor 
was followed by loud explosions, and a rumbling was heard as far south 
as Bloomington, but whether due to the meteor is uncertain. Whether a 
