: 
592 
¥t was formerly termed by Delamethieré 
gisanzte, and still more recently by M. 
Hatiy anathase. M. Vaugquelin has, 
however, found in 1t nothing but the 
oxide of tiéuniuwm, as in the other mi- 
neral denominated red schoerl. 
This fact may be considered as impor- 
tant, since chemistry -had not at that 
time been able to discover any essential 
difference in the composition of these 
two minerals, though their physical 
qualities and their crystallization were 
wholly ditferent. 
A similar example had formerly oc- 
curred in mineralogy. I here allude to 
the arragoniie, in which chemistry dis- 
covers nothing but a carbonate of lime, 
though neither, in weight, hardness, 
fracture, nor crystallization, does it re- 
semble calcareous spar, or common 
carbonate of lune. 
A different example, but which esta- 
bhshes also a species of opposition 
between the phygcal and chemical cha- 
racters of minerals, has occurred during 
the present year.- It is an iron ore, 
known under the name of spathic iron, 
Tt uniformly exhibits the same crystalline 
appearance as carbonated lime, and, in 
like manner, contains a great proportion 
of it. M. Hatiy had arranged it among 
the varieties of this species, considering 
the oxide of iron merely as accidentally 
mixed with it, durimg the crystallization 
of the lime, nearly in the same manner 
as the sand, in the curious crystals of the 
hard grey stone, found sn the forest of 
Fontainbleau. 
It had been indeed long known, that 
the quantity of iron contained in it, is 
extremely variable ; but Messrs. Drapier 
and Descotils have discovered, that the 
proportion of lime varies still more; that 
very frequently it scarcely contains any, 
and that the magnesia, and the oxide of 
manganese, are found in very different 
quantities in different specimens. 
Such are the various combinations 
which occur under the same form. 
These apparent oppositions, concludes 
M. Cuvier, between two branches of the 
game science, or between two modes of 
viewing the same objects, can only pro- 
ceed from some imperfection in the 
‘principles of the one or the other of the 
_two methods, and merit the attention of 
saen of science. . 
The productions of nature are so in- 
timately connected with, and so materi- . 
ally modified by, the climates, in which 
they are found, that noimproyement can 
be made in any of the branches of Natural 
2 
Proceedings of Learned Societies: 
‘hand of man. 
[Suly t; 
. ‘ of 
History, without an exact acquaintancé 
with géography. Hence it appears, that 
this knowledge is scarcely less necessar¥ 
to the naturalist, than to the astronomer 
‘Ttis well known, how much we staid in< 
debted to scientific travellers; and M. 
Olivier has furnished us with new proofs 
of this truth, in a Topographical Account — 
of Persia, which he has just published. 
He describes the chains of the mountains, 
the course of the rivers, and explains the 
nature of the productions by that of the 
climate. By reason of the great drought 
which so generally prevails throughout 
this vast empire, not above a twentieth 
part of it is in a state of cultivation. 
There are many provinces in which not 
a single tree is to be seen, except such as 
have been planted and watered by the 
This evil progressively 
augments by the destruction of the 
canals which conduct the waters from 
the mountains; and the lands being de- 
serted become impregnated with salt, 
which renders them for ever sterile. 
The labours of naturalists who, in= 
stead of exploring foreign countries, pur- 
sue their studies at home, may also prove 
useful to the improvement of geography, 
by suggesting lights calculated to assist 
the inquiries of travellers. ~ 
_ M. de Lacepede, after examining what 
is already known respecting Africa, com- 
paring the size of the rivers which flow 
into the sea, with the extent of the. 
country, on which the rains of the torrid 
zone fall, and with the probable quantity 
of water carried eff by evaporation; for- 
ming, in short, a judgment respecting 
the number and direction of the moun- 
tainous chains in the interior, by those 
with which we are acquainted on ~the 
borders of this great division of the globe; 
from all these circumstances he has 
been led to conjectures respecting the 
physical disposition of the unknowt, re- 
gions in the center, aud particularly in 
regard to the inland lakes and seas, 
which must, he thinks, exist therein. He 
has sketched out the routes which ouglit, 
in his opinion, to be pursued by travél- 
lers, who mtend to explore these yet un- 
discovered countries. og ; 
There is also another Kind of specu- 
lative geography, which. endeayéurs to 
ascertain from the present appearance 
of countries, their state in past times. 
M. Olivier has, we learn: from the pre- 
sent report, investigated in this way, the 
probability of the communication, which 
was formerly supposed to exist between 
the Caspian and Black-Sea. He is of 
opinion 
r 
