456. r Analyses of Books. * ...- [Dec- 
vV.d-—ey.P=A\, | ps 
A 
VL gan =P, 
4 Al \n 
Vile =1- (4), 
1.A'—1.P 
VIII. a—— = ie 
wt — A', then will di-ey= = from whence n = 7. + 
m m i ™ 
—/.(1j—e') = — [(1.m+1.(1 — e')] = period in which the 
population would be reduced “th part. If the population be 
increasing, we shall have by substituting in Art. 3, eae = 
population » years since ; and if decreasing, we have by Art. 5, 
ree: = population nm years since. (See Mr. Milne’s Annui- 
ties, vol. i. P- 103.) 
ARTICLE X. 
ANALYSES OF Books. 
Philosophical Transactions of the Royal Society of London, for 
1922.4) Pare aT. 
We hasten, by our promptitude in the analysis of this part, 
which has just been published, to compensate for our tardiness 
in reviewing the former one. It contains the following papers : 
XIX. Experiments and Observations on the Development of 
Magnetical Properties in Steel and Iron by Percussion. By Wil- 
liam Scoresby, Jun. Esq. (Communicated by Sir Humphry 
Davy, Bart. PRS.) 
“Dr. Gilbert, so early as the year 1600, discovered that iron 
became sensibly magnetic on being hammered and drawn out 
while lying in a north and south direction; ” but Mr. Scoresby 
cannot discover “that any magnetical effect by hammering has 
been produced beyond that of occasioning a deviation in the 
compass needle, or of giving to floating bars or needles the 
power of conforming their position to that of the magnetic 
meridian.” — 
Mr. 8. having already “ succeeded in determining, in a great 
measure, the principal laws by which the development and 
destruction of magnetism in iron by percussion, scowering, 
