18162] ‘ during the Year 1815. 17 
of the revolutions of these magnetic poles are quite erroneous 3 
because he supposes the annual variations equable, which we know 
not tobe the case. Nor have we the least knowledge of the rate at 
which this annual declination varies, and, of course, cannot pre- 
.tend to calculate the periods of revolution. 
VIT. CHEMISTRY. 
The annual progress of chemistry being so much greater than 
that of any of the other sciences, we shall as usual divide it into 
portions, and arrange the facts which we have to communicate 
under different heads, 
I. GENERAL PRINCIPLES. 
1, In the historical introduction to the Annals of Philosophy for 
last year, an account was given of the general principles of the 
atomic theory, An account was also given of a modification of 
that theory by Berzelius, in which he substitutes volumes for atoms ; 
supposing all substances in the first place to be in the gaseous state. 
A very important paper was published ina late number of the 
Annals of Philosophy on this subject. Though the paper in 
question is anonymous, several circumstances enable me to fix with 
considerable certainty on the author; but as he chuses to remain 
for the present concealed, I do not consider myself as at liberty to 
mention his name. The title of the paper is On the Relation 
between the Specific Gravities of Bodies in their Gaseous State, and 
the Weight of their Atoms. (Annals of Philosophy, vol. vi. p. 321.) 
By pointing out this relation, he shows that the two modes of 
viewing the atomic theory come in fact to the same thing. The 
mode of determining the specific gravity of some of the gases 
adopted in this paper deserves attention, as being in all probability 
capable of giving a more accurate result than the methods hitherto 
adopted. 
The author considers atmospherical air as a chemical compound 
of one volume of oxygen and four volumes of azotic gas. It is 
not at all unlikely that this opinion may be correct, though it does 
not coincide exactly with the analyses of air hitherto made. Ac- 
cording to them it is composed of 21 by bulk of oxygen gas, and 
79 of azotic gas. This is undoubtedly a near approximation, and 
if we consider the careless way in which these experiments have 
been made, and the numerous proofs brought. forward by Gay- 
Lussac to show that gases always combine so that one volume of 
one gas unites with one, two, three, or four volumes of the other, 
perhaps we shall be disposed to acquiesce in the conclusion of our 
author, On that supposition he demonstrates, that if the specific 
gravity of air be one, then that of oxygen gas is 1*1111, and that 
of azotic gas 0°9722. This demonstration, however, depends 
upon two suppositions: 1, That an atom of azote weighs 1°75. 
2. That atmospherical air is composed of one atom of oxygen and 
Vor. VII. N°], © B 
