376 
C. BerTuoLvet has prefented to the 
clafs an éxtenfive work upon this fubjecé, 
part of which he previoufly communica- 
ted tothe Inftitute of Egypt. Itproves, 
that, while he fearched for new facts in a 
diftant country, he was equally careful in 
connecting them with fome general theory. 
In enumerating the caufes which alter 
the order of affinity, the firft that may be 
mentioned is the re(peétive quality of each 
of the {ubftances brought into contact. 
Afubftance which remains entirely inac- 
tive whenit enters into acompofitionin no 
greater quantity than the other compenent 
parts, acquires a powerful activity when its 
quantity is augmented. Itwould hence ap- 
pear, that the different parts of each iub- 
fiance uni‘e their efforts to overcome the 
reiftance which is oppofed to them. 
Another ot thefe caufes is the cohefion, 
to a.creater or lefs degree, of one of the 
fimple or compecund iubftances. This 
quality increaies the refiftance to the al- 
teration which the laws of affinity tend to 
produce. . 
A third caufe is elafticity, which dimi- 
nifhes the tendency to combination. Thus 
any fubf#ance, oxygen for example, ats 
wich incomparably greater force wken’con- 
centered in a liquid combination, than 
when in the elaftic ttate. 
The a€tion of heat feems to. enter into 
this third caufes It is probable that the 
mode in which it alters the order of afiini- 
ty in different {ubfiances, is by effecting 
a change in their refpective elaficity. If, 
then, two or more fubétances are found 
when combined together, to produce an 
elafiic, concrete, and perhaps infoluble 
compound, their effect as to the definitive 
vefult muft be calculated according to 
the abfolute power of afhnity poffefled by 
each ingredient ; but an allowance mutt 
be made for the tendency of the concrete 
or elaitic ftate to diminifh their power of 
affinity. . 
The application of thefe. principles, 
which had not before been confidered’ in 
a general point of view, muft greatly tend 
to. elucidate all the phenomena ot. che- 
nifiry. 
C. BERTHOLLET hasaccordingly been 
able, by means of. thofe, principles, to 
bring within. the compafs of the known 
laws of chemiftry a multiplicity of. facts 
which.appeared unconneéted with, or even 
contrary to, thole laws. 
Hitherto, for example, the affinities of 
the greateit part of compound bodies were 
regarded as independent of their compo- 
nent parts, becaufe the circiimftances 
above-mentioned were nevey taken into 
calculation, 
National Tiftitute. 
[ May qr, 
But C. BERTHOLLET clearly proves, 
that in a variety of inftances, the former 
depend upon the latter, and fhews how — 
from fo fmall a number of elementary fab- 
ftances are formed fo many compounds, 
and the infinitely varied effects which na- 
ture prefents to the view of the chemical 
inguirer. . 
Thote happy explanations which re- 
move anomalies and apparent paradoxes, 
are always received with pleafure by the 
philofopber, becaufe they relicve his. mind 
from that perplexity which is infupperta- 
ble to the pride of man.” 
Belide the table, which I have already 
mentioned, C. Guyton has prefented 
us with four others. which he has drawn 
up for the elementary inftruétion of the 
pupils of the Polytechnic School. 
One contains the methodical diftribu- 
tion cf the mincrals into orders, ciafles, 
genera, and fpecies. Another gives a 
complete fyftem of the external charaéter- 
iitics of minerals, according to the prin- 
ciples of Werner. 
laft is to render eafily intelligible to be- - 
ginners, C. Hauy’s theory of the forma- 
tion of cryftals, by prefenting,in order 
the firft molecule of a cryftal, its nucle- 
us, and the different modifications pro- 
duced by the laws of diminution in the 
foivent, and by giving them drawings 
explanatory of the formule which repre- 
fent thefe modifications, and the folids 
refulting fromthem. ~ - 
This zeal for propagating the difeco- 
veries of another, would have been re-. 
marked at atime when a natural jealoufy 
fo often prevailed among thofe who af- 
pired te any reputation for fcience. But 
at prefent, when thofe who cultivate 
knowledge are all united by the ties of a 
noble friendfhip, this circumf{ance can no 
ionger form the fubject of eulogium. 
Several naturalifts of the clafs have 
been occupied, vuring the preceding, 
quarter, in examining the wrecks of thole 
organic bodies which are difcovered in _— 
places where anzlogous objects no longer . 
exift—an inquiry of the highelt import-. 
asce to the curiofity of, man; who, not: 
fatished with endeavouring to élucidate 
his own hiftory, attempts to penetrate 
that of the globe, compared with which 
fcience has: fcarcely exifted for a fingle day. 
Cy Vitiaks, an affociate, has inform- 
ed us that he difcovered pieces of fofiile 
wood on one of the higheft mountains of 
the Alps, at the foot of a glacier, which 
is more than 760 metres* in perpendicu- 
lar height above the neareft forefis now 


* 3 fect 11 inches old French meafure. 
‘ remaining. 
The object of the two * 
Co ee 


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