1823.} 
causes may tend to influence the eqni= 
librium, the figure or motion, ,of the 
earth ; these physieal conditions, which 
had not been hitherto introduced into 
any theories of the globe, will throw 
light on different questions of geology 
and general physics. 
“The “ Analytical Formule” of M. De 
la Place, have led to the following re- 
sults. The couches or lays, at the 
greatest depths, are the most dense. 
These couches are regularly disposed 
about the centre of gravity of the globe, 
and they differ but little, in point of 
form, from that of a curved surface, 
formed by the revolution of an ellipsis. 
-The density of the water is nearly five 
times less than the mean density of the 
earth. The heaviest rocks have not 
the mean density of the glcbe at large, 
and of course the interior couches are 
not of the same nature as the surface. 
The presence and distribution of the 
waters on the surface of the earth pro- 
duce no considerable change in the 
law of the diminution ‘of the degrees, 
and in that of gravity or weight, Every 
geological system, founded on the hy- 
pothesis of any considerable displacing 
of ihe poles, at the surface of the earth, 
must, be inconsistent with the mecha- 
nical causes now ascertained to deter- 
mine the figure of the earth. The 
temperature of the globe has not, sen- 
sibly, diminished, since the time of 
Hipparchus, (more than iwo thousand 
years,) and the cffect of this decrease of 
heat has made no variation in the whole 
of this time, in the duration of a day, 
the two-hundredth part of a centesimal 
second. 
M. Girard has employed himself in 
investigating certain questions relative 
to cast iron, and the use of that mate- 
rial in machinery; also as to the con- 
ducting of waters, and to the coppers of 
steam-engines. ‘The casting of iron 
may be readily adapted to the form 
which nature impresses on bodies, to 
render them capable of a determinate 
resistance, with the least. possible 
quantity of resisting matter. And thus 
the figure of hollow pipes may be given 
to different mobile pieces of a machine, 
while casting, like to the stalks of cer- 
tain plants, ar to the plumage of birds. 
M, Girard, who is also author of an 
excellent “Treatise on the Resistance 
of Solids,” deduces from his “ Pormulz” 
the relation between the interior and 
exterior diameters of a hollow cylinder, 
so as to render the eylinder both lighter 
and more capable of resistance, in given 
Proceedings of Public Societies. 
determinate weight of baggage. 
24% 
circumstances. ‘The facts cited by the 
amthor, the details into which he enters 
relative to the operations of casting, 
and also to the means of augmenting 
solidity and preducing uniformity there- 
in, are well worthy the notice and study 
of artists. 
M. Dupin recited a report on the 
construction of carriages, and on the 
causes that render them most liable to 
be overturned. One of these, perhaps 
the principal, is neglecting the execu- 
tion of ihe ordnances as to the loading 
of carriages. The conditions, or cases 
‘of stability of a carriage in motion, ac- 
cording to the nature, the inclination, 
and the greater or less perteetion of the 
roads, are considered; but the reporter, 
without pointing out new forms or me- 
thods, lays down data to discover and 
ascertain them. He refers to the pro- 
gress which it is natural to expect, from 
the growing improyement of the me- 
chanical arts, applied to the construc- 
tion of carriages. "These are capable of 
being made lighter, without impairing 
their solidity, and better able to en 
counter hazards, without diminishing 
their firmness. Improvements, also, 
must be pianned, as to the form, struc- 
ture, and keeping up, of roads; and 
regulations must be rendered more 
efficacious to produce their effect. 
The author recommends to the go- 
verament to propose a prize of twent 
thousand frances, fo be granted on the 
first of January 1825, to the constructor 
or coach-maker, that, without neglect- 
ing such qualities as are requisite in a 
public carriage, capacity, convenience, 
and lightness, shonld secure, also the 
ereatcst stability for the conveyance of 
a given number of passengers, with a 
it 
will require the experience of a year or 
two, to. prove the goodness of such 
carriages. ‘The plans of the carriages 
should be accompanied with a descrip- 
live memoir, detailing the calculations 
as fo stability. Ina program should be 
accurately specified certain facts io 
serve as bases to the attempts of pro- 
jecting mechanists, including fixed 
principles, from which the proportion of 
carriages may be derived, as also the 
best disposition of the loading, so as to 
acquire the greatest possible stability. 
The same reporter, as the organ or 
representative of the. commission de- 
puted to examine the work of M. 
Maresticr, on steam-packets, and the 
military'marine of the United States of 
America, detailed the contents of their 
analysis, 
