380 Analyses of Books. [Nov. 
This admirable paper is printed entire in the last number of 
the Annals.* 
XII. On the Expansion in a Series of the Attraction of a Sphe- 
roid. By James lvory, MA. FRS. 
This elaborate paper does not admit of profitable abridgment. 
The author suggests, in the conclusion, that Laplace’s theory of 
the figure of the planets “ will probably be found to hinge on 
this proposition, that a spheroid, whether homogeneous or hete- 
rogeneous, cannot be in equilibrium by means of a rotatory 
motion about an axis, and the joint effect of the attraction of 
its own particles, and of the other bodies in the system, unless 
its radius be.a function of three rectangular co-ordinates.” 
XII. On the late extraordinary Depression of the Barometer. 
By Luke Howard, Esq. FRS. 
Mr. Howard has already stated the amount of this remarkable 
depression in the Annals for February last, p. 160. Among other 
observations respecting it in this paper, which is illustrated by a 
plate of the autographic curve of the barometric variations, are 
the following: “ It will be seen that this great depression was 
preceded by abrupt changes, fluctuating for 30 days, chiefly 
between 29°5 and 30 inches, during a continuance of stormy 
weather; and that the depression itself was 14 or 15 days in 
progress from the point of 30 inches, to that from which it finally 
rose in three days. The rain for these two months is 10°10 
inches, a quantity without precedent in the same space of time 
at London ; that is to say, without one on record.” 
XIV. On the anomalous Magnetic Action of Hot Iron between 
the White and Blood-red Heat. By Peter Barlow, Esq. of the 
Royal Military Academy. (Communicated by Major Thomas 
Colby, of the Royal Engineers, FRS.) 
Certain theoretical results relative to the magnetic action of 
iron, obtained by Mr. Bonnycastle, induced Mr. Barlow to ascer- 
tain the relative attraction which different species of iron and 
steel had for the magnet. The following are the results of his 
experiments for that purpose, assuming the tangents of the 
angles formed by the deviation of the needle when acted upon 
by equal-sized bars of the several descriptions of metal placed 
* The following investigation of the same subject by a method entirely different from 
Dr. Wollaston’s, has been pointed out in a contemporary Journal : 
‘¢ The highest portions of the atmesphere, which is carried round in 23 hours and 56 
minutes, by the rotation of the earth about its axis, would be projected into space, if 
their centrifugal force at that distance were not less than their gravitation towards the 
centre. But the centrifugal force is directly as the distance, while the power of gravity 
is as its square. Consequently when the centrifugal force at the distance of 6:6 radii of 
the earth is augmented as many times, the corresponding gravitation is diminished by 
its square, or 43°7 times, their relative proportion being thus changed to 289. Now the 
centrifugal force being only the 289th part of gravity at the surface of the equator, it 
will, therefore, just balance this power at the distance of 66 radii from the centre, or at 
the elevation of 22,200 miles.”-—( Leslie on Meteorology, Supplement to the Encyclo- 
pedia Britannica, vol. v. p. 325.) 
