476. 
from one medium into another of a diffe- 
reut density, aud that the degree of re- 
fraction is im a direct ratio fo the density 
of the body if incombustible, but in- 
creasing in proportion to the combustibi- 
“lity of the body through which it passes. 
Hence Newton divined the combustibi- 
hty of the didmond, and the existence of 
a combustible principle in water. 
If two substances be mixed together, 
the proportion of whose refracting pow- 
ers.is known, and regard be paid to the 
density of the mixture, we shal! be there- 
by enabled to calculate the total refrac- 
tion; and reciprocaily, when the refrac- 
tion of a mixture is ascertained, of which 
the elements are known, we may, in like 
manner, calculate the proportional re- 
fracting power of each. M. Biot having 
apphed this principle to mixtures of 
known proportions, and having found it: 
just, afterwards applied it to ascertain 
the unknown proportions of other mix- 
tures. ; ; 
For this purpose it is sufficient to fill 
“a glass prisin, under a known pressure, 
with the substance we wish to examine, 
or if it bea solid body, to form it into a 
“prism itgelf, and observe through ‘it a dis- 
taut oliject. The angle of refraction is 
Proceedings of Learned Societies. 
[June I, 
By this experiment atmospheric air gave 
exactly that degree of refraction which 
ought to be produced, according to eal- 
culation, by a mixture of 0,21 oxygen, 
0,787 azot, and 0,003 of carbonic acid. 
Even when these gases were not in the 
State of a simple mixture, but brought 
into the most intimate combination with 
each other, the same principle was found 
equally applicable, provided no very 
considerable condensation had been pro- 
duced. Ammoniacal gas produced the 
effect indicated by the quantities of azot 
and hydrogen, which enter into its com- 
position ; but when too much condensed, 
some alteration, though very trifling, was 
observable; the same circumstance oc- 
curred in the €xperiment with water. 
An accurate examination of the muri- 
atic acid gas, according to these principles, 
fully demonstrated that its radical could 
not be azot, and consequently that this 
gas cannot be considered, as has been 
lately supposed, an oxyde of hydrogen 
containmeg less oxygen than water. 
The refractive property of the dia- 
inond beiug much greater than that of 
charcoal, the refractions of the carbonic 
acid, alcohol, ether, aud other substances, 
of which carbon forms a part, M. Biot 
measured by the repeating circle, taking -concludes that the diamond cannot be a 
into account the weight, tne tempera- 
“ture, and the ‘humidity of the external 
‘air; and this inethod being susceptible of 
a decree of precision equal to that of 
astronomical processes, necessarily sur- 
passes in accuracy all the chemical means 
“employed with the same intention. But 
it will readily be perceived that this mode 
is only applicable to transparent sub- 
“stances, and the principles of which, as 
far as reyards their species, are known to 
as. 
M. Cuvier next proceeds to. pomt ovt 
the great utility of this discovery, and in- 
forms the Institute that the author has 
already applied it to the aualysis of gase- 
‘ous bodies, and obtained by this means 
the most important results, of which the 
following are among the most interest- 
Hig :— : 
“At an equal degree of density, oxygen 
possesses the least, and hydrogen the 
greatest refractive power among all the 
vaseous bodies. The refractive powers 
of the samme vas is in an acurate pro- 
portion to its density, under an unitorm 
temperature, [te is to the presence of 
bvdrogen, in particular, that substances 
possessing a high degree of retracting, 
power appear to owe this property, since 
it was found to be present in all of them. 
pure charcoal, arid that a fourth part of 
hydrogen, at least, is necessary, in order 
to render it conformable to the results of 
the experiment. , 
The matters produced by organized 
beings have not: hitherto been examined 
with sutheient accuracy. For although 
we have a general knowledge of the ele- 
ments of which they are composed, aud 
that these primitive elements are not 
very humerous, yet their combinations are 
so various, and they are so easily changed 
and converted in the course of the expe- 
riment, that it is necessary to study these 
combinations themselves as if they. were 
simple substances. ‘These matters coi- 
sidered under this point of view, are 
termed the inunediute principles of orgun- 
ized bodies; and during the present year 
several of them, we learn ftom M. Cu- 
vier, have been discovered by dierent 
French chemists. -Among others he 
mentions M, Vanquelin and Robiquet, 
who have found in the sap of asparagus, 
a crystaline matter, soluble in water, 
which is, however, neither an acid, nor a 
neutral salt, and which is not acted upon 
by the usual re-agents. These cele- 
brated chewists propose to follew out the 
Investigation of this substance, and in 
due tine io lay the result of their labours 
before 
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