ADH 
ADH 
as weights, being each of them four grains. 
Thit species must be raised on a hot-bed 
from seeds. It has never flowered in Eng- 
land : it is of very slow growth. The other 
species, viz. the A. falcata, and A. scandens, 
have not been cultivated in this country. 
ADENIA, in botany, a genus of the Hex- 
andria Monogynia class and order, that 
growk in Arabia. There is but one species, 
which is mentioned by Forskal, in his Flor. 
/Egypt. He says that the powder of the 
young branches mixed in any kind of liquor 
is a strong poison, and that the capparis spi- 
nosa is an antidote to it. 
ADFECTED equations, in algebra, those 
wherein the unknown quantity is found 
in two or more different powers : such is 
■r 3 — ax 2 b x — a 2 b. 
ADHESION, in philosophy and che- 
mistry, is a term generally made use of to 
express the property which. certain bodies 
have of attracting to themselves other bo- 
dies, or the force by which they adhere to- 
gether: thus, water adheres to the finger, 
mercury to gold, &c. Hence arises an im- 
portant distinction between two words, that 
in a loose and popular sense are often con- 
founded. Adhesion denotes an union to a 
certain point between two dissimilar sub- 
stances, and cohesion that which retains to- 
gether the component particles of the same 
mass. See Cohesion. 
Adhesion may take place either between 
two solids, as two hemispheres of glass, which, 
according to an experiment of Desagulicrs, 
adhere to each other with a force equal to 
19 ounces on a surface of contact one-tenth 
of an inch in diameter ; or between solids 
and fluids, as the suspension of water in ca- 
pillary tubes ; or lastly, between two fluids, 
as oil and water. About the same time 
Mr. Hauksbee proved experimentally the 
error which Bernoulli had fallen into, in at- 
tributing the adhesion of surfaces and capil- 
lary attraction to the pressure of the atmos- 
phere^ Nevertheless, in 1772, M. M. La- 
grange and Cigna, taking for granted a na- 
tural repulsion between water and oily 
substances, imagined, if there was an adhe- 
sion between water and oil, or tallow, that 
it must be occasioned by a cause different 
from attraction : and having ascertained the 
reality of the adhesion, they concluded that 
it was occasioned by the pressure of the air, 
and that Dr. Taylor’s method was not well 
founded. 
Such was the state of opinions on the sub- 
ject, when, in 1775, Guyton Morveau made 
his celebrated experiments on adhesion, in 
presence^ of the Dijon Academy, demonstrat- 
ing, as indeed Hauksbee had done before 
him, not only that water ascends between 
two parallel plates of tallow, separated from 
each other J of a line, but also that the at- 
mospheric pressure is not in the least degree 
the cause of the phenomenon, which is solely 
attributable to attraction : in proof of this, 
a polished disk of glass, 30 lines in diame- 
ter, was suspended to the arm of a balance, 
and brought into contact with a surface of 
mercury ; the counterpoise required to sepa- 
rate it was equivalent to 9 gros and a few 
grains, and upon moving the apparatus into 
the receiver of an air-pump, and forming as 
perfect a vacuum as possible, precisely the 
same counterpoise was required as before. 
In the prosecution of his inquiries on this 
subject, he observed, that the same disk of 
.glass, which, when in contact with pure 
water, adhered to it with a force equal to 
258 grains, required a counterpoise of only 
210, in order to separate it from a solution 
of potash, notwithstanding the superior den- 
sity of this last. This inequality of effects 
on equal diameters, and in an inverse order 
to that of the respective specific gravities of 
the two fluids, appeared not only to be de- 
cisive in favour of Dr. Taylor’s method, but 
to encourage the hope of applying it to the 
calculation of chemical affinities. 
In order to verify this proposition, plates 
of the different metals in their highest state 
of purity were procured, perfectly round, an 
inch in diameter, of the same thickness, well 
polished, and furnished with a small ring in 
the centre of each, so as to keep them sus- 
pended precisely parallel to the plane of the 
horizon. Each of these plates was in turn 
suspended to the arm of an assay balance, 
and exactly counterpoised by weights placed 
in the scale attached to the opposite arm ; 
the plate, thus balanced, was applied to the 
surface of some mercury in a cup, about two 
lines beneath it, by sliding the plate over the 
mercury as in the silvering of mirrors, so as 
to exclude every bubble of air; weights 
were then successively added, till the adhe- 
sion between the plate and mercury was bro- 
ken. Fresh mercury was used for each experi- 
ment. The following is the table of results : 
Gold adheres to mercury with 
a force equal to., 446 grains, 
Silver 429 
Tin 418 
Lead 397 
Bismuth,,.!.. 373 
