444 
what effects must result from the action 
of terrestrial magnetism, combined swith 
that of the. conductors, -It explains.a 
remarkable fact, first: observed by MM. 
Faradai, and which consists in the con- 
stant motion. of a portion of the’ con- 
ductor about a magnet. . The explica- 
tion serves to complete the experiment, 
and has suggested the turning of the 
magnet about its axis, and producing a 
constant motion between the conductors. 
The author of this theory, M. Ampere, 
has, deduced from his observations the 
mathematical expression of the: force 
that acts between the elements of the 
couductors,, aud thereby reduces to a 
siitle principle the most complicated 
effects of the action of the conductors, 
and , of, terrestrial magnetism. Our 
limits will not allow of particularizing 
the results of some fine experiments of 
Sir Hw Davy, on the measure of the 
condueting. property which different 
metals..possess, when traversed by the 
electric currents. For the same reason, 
we canjonly mention a’ process of M. 
Schweiger, for multiplying and render- 
ing manifest the effects of an electro- 
motive forge, ‘that appears to be in a 
manner insensible. 
M. Biot and M. Poiullet haye been 
also inyestigating the action of conduc- 
tors on magnets, for the purpose of de- 
termining, its mathematical laws by a 
correct, process. Messrs. Savary and 
de. Montferrant haye produced some 
successful applications of the integral 
caleulus to the measure of electro-dyna- 
mic effects ; and have deduccd from the 
law, set forth by M. Ampere, results con- 
formable to the experiments of Cou- 
Yomb, and others already cited. 
“From some recent experiments of M. 
Seeback,. of. the Academy of Berlin, we 
learn, that, the, contact of different me- 
tals, and the inequality of temperatures, 
will be sufficient to produce very'sensible 
magnetic effects. The alternate succes- 
sion of ;two metals retained to unequal 
temperatures, augments effects of this 
kind, and, so to. speak, multiplies them 
to am indefinite extent.. M. Oersted 
has just’ discovered some remarkable 
properties of thcse\actions, to which be 
givesithe naine of thermo-electrival. 
‘Dbis sketch, though rapid and imper- 
feet, may, However, let us into the whole 
extent of thesenew theories. A relation 
so manifest, between: phenomena: that 
might well be thought of a totally differ- 
ént nature, proyes to.us that they havea 
common. origin, ‘and fartishes hints to 
speculate on the cause of terrestrial 
“ “ 
Proceedings of Public Societies. 
[Dec. 1, 
magnetism, and its relations with the 
aurora Horealis:! | As very intense! mag- 
netic effects are determined only by'the 
diversity of the’ matters put in contact, 
and by the difference of témperatnres; 
similar effects will doubtless: be’ ob-' 
served in the'solid envelope of ‘tlie ter~ 
restrial globe; and, at the same time, 
the influence of diurnal or annual varia- 
tions of heat produced by the solar 
rays, will be illustrated. ' 
In the’ great work) called‘ Celestial 
Mechanics,’ the author had ‘annoanced 
his intention of drawing up am hist6rical 
summary of all such mathentaticaldis- 
coveries as have a relation to the system 
of the world. The first part of this his 
tory has just appeared ; an cleganit pre- 
cision pervades this performance, similar 
to what is observed in the'* Notice des 
Progrés de l’ Astronomie.’” ctl 
The first part of the fifth volame’ is 
occupied with mathematical researches 
on the figure of the earth.’ This ‘very 
difficult question is now’ completely 
resolved. Jeet tO 11103 
Tn treating of thé mutual action of the 
splieres, the author examines the ‘condi* 
tions of the molecular statics of aériform 
fluids. This part of his investizations is’ 
entirely novel.’ The ‘Analysis of Mode 
La Place explains the two' known liws 
of the statics of gases. ‘One of these 
laws bears the name of Mariotfe, who 
discovered it; for the second, we are it- 
debted to Messrs. Gay-Lussac and 
Dalton. . 
In this same analysis we may’ trace, 
very distinetly, the conditions that’ give 
a determination to solidity, to liquids, 
to conversions into vapour, and to any 
intermediate state of vapours very muchi 
condensed. ‘These were points not well 
known till ascertained in ‘the experi- 
ments of Le Baron Cagniard’ de Ja 
Tour. 
The same theory gives the exact mea- 
sure of the velocity ef sound in the air, 
a very ancient ‘question, which bad 
hitherto been but imperfectly resolved, 
as the elevation of temperature,'to be 
considered along with the compression 
of the air, had not) till then, been 
observed. de Pid 
The French academicians, in 1738, 
had» made some ‘experiments for mea=" 
suring’ this’ velocity;' the Board” of 
Longitude reneweil them, in the month’ 
of June last, with wl possible precision: 
It has been found that the velocity of 
sound; in the air;'at the timnbabatnre! bf 
55° Fahrenheit; differs very little from 
1044 feet per second. ‘Phe correctness 
of 
