OSM 
would fall throngh its chord, as the semi- 
circle to the diameter. 4. The times of 
the oscillations in cycloids, or in small 
arches of circles, are in ^ sub-duplicate ra- 
tio of the lengths of the pendulums. 5. But 
it the bodies that oscillate be acted on by 
unequal accelerating forces, then the oscil- 
lation will be performed in times that are to 
one another in the ratio compounded of the 
direct sub-duplicate ratio of the lengths of 
the pendulums, and Inverse sub-duplicate 
ratio of the accelerating forces. Hence it 
appears, that if oscillations of unequal pen- 
dulums are performed in the same time, the 
accelerating gravities of these pendulums 
must be as their lengths; and thus We con- 
clude, that the force of gravity decreases as 
you go towards the equator, since we find, 
that the lengths of pendulums that vibrate 
seconds, are always less at a less distance 
from the equator. 6. The space described 
by a falling body in any given time, may be 
exactly known : for, finding by experi- 
ments, what pendulum oscillates in that 
time, the half of the pendulum will be to 
the space required, in the duplicate ratio of 
the diameter of a circle to the circumfe- 
rence. 
OSIER, a very valuable shrub, of the 
Salix viininales, used principally in bas« 
ket making. 
OSMITES, in botany, a genus of the 
Syngenesia Polygaraia Frustranea class and 
order. Natural ol der of Composit® Dis- 
coidete. Coiymbifer®, Jussieu. Essential 
character : calyx imbricate, scariose ; co- 
rolla of the ray ligulate; down obsolete; 
receptacle chaffy. There are four species, 
all shrubs, and natives of the Cape of Good 
Hope. 
OSMIUM, one of the metals discovered 
by Mr. Tennant, in the black powder which 
remained after dissolving platina : the other 
metal was Irididm, which see. The os- 
mium was obtained by heating the black 
powder with pure alkali in a silver crucible. 
The oxide of this metal combines with the 
alkali, may be expelled by an acid, and, be- 
ing very volatile, may be obtained by dis- 
tillation. It does not redden vegetable 
blues, but stains the skin of a deep red or 
black. The oxide, in solution with water, 
has no colour; but by combining with al- 
kali or lime, it becomes yellow. With the 
infusion of nut-galls, it gives a very vivid 
blue colour. It is precipitated by all the 
metals, excepting gold and platina. An 
amalgam may be formed with mercury, by 
agitating it with the aqueous solution of this 
OST 
oxide. When this amalgam is heated, the 
mercury is driven off, and the pure metal 
remains behind in the state of black pow- 
der. This metal was called osmium on ac- 
count of the strong smell of the oxide. 
OSMUNDA, in botany, a genus of the 
Cryptogamia Filices class and order. Na- 
tural order of Filices or Ferns. Generic 
character : capsules distinct, disposed in a 
raceme, in such a manner as to look the 
same way, or else heaped on the back of 
the pinna or division of the frond, sessile, 
sub-globular, opening transversely without 
any ring ; seeds very many, extremely mi- 
nute. There are twenty-seven species. 
OSSIFICATION, the formation of bones, 
but more particularly the conversion of 
parts naturally soft, to the hardness and 
consistence of bones. All concretions which 
make their appearance in the solids of the 
animal body may be comprehended under 
this title with propriety, because they have 
a close resemblance to, and composed of si-, 
milar constituents with Bone, which see. 
In the pineal gland concretions have been 
found, which consist of phosphate of lime. 
The same is true of concretions found in the 
salivary glands, in the prostate, and in the 
liver ; and also in pulmonary concretions. 
Ihe latter . however are found to contain 
phosphate and carbonate of lime, and in 
some cases no phosphate, but 
Carbonate of lime 82 
Animal matter and water 18 
100 
OSTEOLOGY, that branch of anatomy 
which treats of the bones. 
OSTEOSPERMUM, in botany, a genus 
of the Syngenesia Polygamia Necessaria 
class and order. Natural order of Compo- 
sit® Discoide®. Corymbifer®, Jussieu. 
Essential character : calyx simple, or in two 
rows, many-leaved, almost equal ; seeds 
globular, coloured, bony ; down none ; 
receptacle naked. There are seventeen 
species. 
OSTRACION, the trunk Jish, in natural 
history, a genus of fishes, of the order Car- 
tilaginei. Generic character : teeth cylin- 
diic, pointing forwards and rather blunt ; 
body mailed by a complete long covering. 
There are twelve species. We shall notice 
only the O. triqueter, or the triangular 
trunk fish, is about twelve inches long, 
and is completely, except to a very short 
distance from the tail, surrounded with a 
bony covering, divided into hexagonal 
