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POPULAR SCIENCE REVIEW. 
by Mr. Denning ; and in the second place if they had, it is certain that the 
observed effects would not be those on which Mr. Denning bases his theory. 
If the radiant of a meteor system in January, for instance, is precisely the 
6ame as the radiant of a meteor system in April, then it is certain that the 
first meteor system and the second meteor system are altogether distinct 
from each other. For the direction of the earth’s motion, on which of neces- 
sity the position of a radiant depends largely, has changed in the interval 
through one quadrant, that is to say, the earth in April is travelling at right 
angles to the direction she had in January — the same being true of any 
two periods in the year separated by three months. Capt. Tupman, who 
very promptly indicated, at the meeting where Mr. Denning’s paper was 
read, the utter incompatibility of Mr. Denning’s theory, either with possi- 
bilities or with the facts on which Mr. Denning attempted to base it, has 
supplied some “ remarks on Mr. Denning’s paper,” which immediately follow 
it (we are glad to see) in the 11 Monthly Notices,” and in some degree save 
the Royal Astronomical Society from the discredit which papers presenting 
untenable and unscientific theories tend to bring upon it. 
Transit of Mercury. — A transit of Mercury occurs on May 6. For centre 
of earth the times of contact are as follows — 
External impact at ingress 
Internal „ „ 
Least distance of centres, 3' 47"*4 . 
Internal impact at egress 
External „ „ 
Angle from North Pole for direct image — 
Contact at ingress .... 
„ „ egress .... 
Mean time at G-reenwich. 
h. m. s. 
May 6 3 12 25 
3 15 32 
7 0 4 
. 10 44 34 
. 10 47 43 
. 45° towards E. 
. 100° „ W. 
As the sun sets at 7h. 28m., little more than the first half of the transit 
will be visible in this country. 
Other Phenomena for the Quarter. — Venus will be at her greatest westerly 
elongation at 6 a.m., May 2 ; Mercury at his greatest westerly elongation at 
7 p.m., June 2. None of the superior planets come into opposition during 
the quarter. 
CHEMISTRY. 
The Hydrocarbons formed by the Action of Acids on Spiegeleisen. — Oloez 
has examined the products resulting from the action of dilute hydrochloric 
acid (spec, gravity = 1*12) on soft cast-iron containing 004 per cent, chemi- 
cally combined carbon, and about 0*06 per cent, manganese. As some of 
the hydrocarbons enter into combination with this acid, sulphuric acid 
diluted with five times its weight of water was subsequently used. In one 
experiment 200 kilog. of iron were treated with acid, and this quantity 
yielded 1*64 gramme of oily hydrocarbons condensed in the first washing- 
bottle •, 2*278 grammes of brominated hydrocarbons of the ethylene series ; 
3*632 grammes of hydrocarbons of the marsh gas series separated by means 
of sulphuric acid ; 4*38 grammes of solid residue ; and 5*408 grammes of 
