H Y D 
H Y D 
H Y D 
forcing-pump C, being three inches in dia- 
meter. 
D is an iron cylinder attached to the pump- 
rod, which passes through it: such cylinder 
is filled with lead, and weighs about 240 lbs. 
This. power works the pump, and forces the 
water to ascend to the house through a pipe 
one inch in diameter, and which is 420 feet 
in length. 
At E is fixed a cord, which, when the 
bucket approaches to within four or five 
inches of its lowest projection, extends, and 
opens a valve in the bottom of the vessel 
through which the water is discharged. 
An engine in a great degree similar to this 
was erected some years ago by the late James 
Spedding, esq. fora lead mine near Keswick, 
with the addition of a smaller bucket which 
emptied itself into the larger near t lie begin- 
ning of its descent, without which addition it 
was^found that the beam only acquired a liora- 
ratory motion, without making a full and ef- 
fective stroke. 
To answer this purpose in a more simple 
way, Mr. Sarjeant constructed the small en- 
gine in such manner as to finish its stroke 
(Speaking of tiie bucket end) when the beam 
comes into an horizontal position, or a little 
below it. By this means the lever is virtu- 
ally lengthened in its descent in the propor- 
tion of the radius to the cosine, of about 30 
degrees, or as seven to six aearly, and conse- 
quently its power is increased in an equal 
proportion. 
It is evident, that the opening of the valve 
might have been effected, perhaps better, by 
a projecting pin at the bottom, but Mr. S. 
chose to give an exact description of the en- 
gine as it stands. It has now been some years 
in use, and completely answers the put pose 
intended. 
The only artificers employed, except the 
plumber, were a country blacksmi h and 
carpenter; and the whole cost, exclusive of 
the pump and pipes, did not amount to 5/. 
Pumps are engines depending also on the 
principles of hydraulics. See I ump. 
HYDRO-CARBONATES, combinations, 
of carbon with hydrogen. A gas of this name 
is obtained from moistened charcoal by dis- 
tillation. 
HYDROCELE. See Surgery. 
I 1 YD ROCIIA RIS, the lUlleimtcr-Uly , a 
genus of the enneandria order, in thedicccia 
class of plants, and in the natural method 
ranking under the first order, palmax The 
spatha of the- male is diphyilous; the calyx 
■ trifid; the corolla tripetalous; the three inte- 
rior filaments styliferous. The female cahx 
trifid; the corolla tripetalous ; the styles six ; 
the capsule has six cells, and is polvspermous 
inferior. There is only one species, a native 
of Britain, growing in slow streams and wet 
ditches. It has kidney-shaped leaves, thick, 
smooth, and of a brownish- green coloui, with 
white -blossoms. I here is a variety with 
double flowers, of a very sweet smell. 
II YD ROCOTYLE, ivater-navd wort, a 
genus of the digynia order, in the pent n- 
dria class of plants, and in the natural me- 
thod ranking under the 45th order, umbel- 
late. The umbel is simple; the invoke rum 
tetraphy lions; the petals entire; the seeds are 
half round and compressed. There are 15 
species, none of which are ever cultivated in 
gardens. One of them, a native of Britain, 
growing in marshv grounds, is supposed by 
the farmers to occasion the rot in sheep. The 
leaves have central leaf-stalks, with about five 
flowers in a rundle ; the petals are of a reddish 
white 
HYDROGEN, in chemistry, one of the 
simple combustibles, the base' of hydrogen 
gas, formerly called inflammable air. 
HYDROGEN-GAS. To obtain this, 
put one part of iron-filings into a retort, at- 
tached to the pneumatic cistern, and pour 
thereon two parts of sulphuric acid previously 
diluted with four times its bulk of water. Im- 
mediately the mixture begins to boil or effer- 
vesce with violence, and air-bubbles rush 
abundantly from the beak of the retort. Al- 
low 7 them to escape lor a little, till you sup- 
pose that the common air which previously 
filled the retort has been displaced by the 
newly generated air. Then place an inverted 
jar over the beak of the retort. The bubbles 
rush in abundantly and soon fill the jar. 
It was obtained by Dr. Mayow and by Dr. 
Hales from various substances, and had* been 
known long before in mines under the name 
of the fire-damp. But Mr. Cavendish ought 
to be considered as its real discoverer; since 
it was lie who first examined it, and pointed 
i out the difference between it and atmospheric 
! air, and who ascertained the greatest number 
of its properties. 
Hydrogen gas, like air-, is invisible and 
i elastic, ainl capable of indefinite compression 
I and dilatation. Its specific gravity differs ac- 
! cording to its purity 7 . Kirwan found it 
j 0.00010; Lavoisier 0.000094, or about 12 
I times lighter than common air. All burning 
j substances are immediately extinguished by 
! being, plunged into this gas. It is incapable 
j therefore of supporting combo.stion. Small 
; animals, when they are obliged to breathe it, 
die; but large animals resist its action longer. 
Scheele found that he could breathe it for 
some time without much inconvenience; but 
Fontana, who repeated the experiment, 
affirmed that this was owing to the quantity 
of common air contained in the lungs when 
he began to breathe; for on expiring as 
strongly as possible before drawing in the hy- 
drogen gas, he could only make three respi- 
rations, and even these three produced ex- 
treme feebleness and oppression about the 
breast. 
The ingenious Mr. Davy, professor of che- 
mistry in the Royal institution, to whom w 7 e 
are indebted for many curious and important; 
but rather hazardous experiments on respira- 
tion, made chiefly upon himself, after a com- 
plete exhaustion of his lungs, found great 
difficulty in breathing this gas for so -long as 
half a minute. It produced uneasy. feelings 
in the chest, momentary loss of muscular 
power, and sometimes a transient giddiness. 
Pilatre de Rozter publicly verified the as- 
sertions of Scheele. lie breathed hydrogen 
gas six or seven limes from a bladder w ithout 
inconvenience. To demon trate that it was 
really hvdrogen gas which lie was breathing, 
he made a strong inspiration, and expired the 
air slowly through a long tube. On bringing 
a lighted taper to ttie end oi the tube, the gas 
took fire, a: d continued to burn for some 
time. It was objected to him, that the gas 
which he breathed was diluted with common 
air. To shew that this was not the ease, he 
mixed together one part of common air and 
nine parts of hydrogen -gas, -and having drawn 
9-*9 
the mixture into his lungs, he threw it out the 
same w ay. On applying a taper to die tube, the 
whole oi the gas exploded in his mouth, and 
almost stunned him. At first he thought that 
the whole of his teeth had been driven out, 
but fortunately he received no injury what- 
ever. 
If a phial is filled with hydrogen gas, and 
a lighted candle brought to its mouth, the 
gas will take fire, and burn gradually, till it is 
all consumed, if the hydrogen gas is pure, 
the flame is of a white colour ; but if the gas 
holds any substance in solution, w hich is- ottea. 
the case, the flame is tinged of different cq*~ 
lours, according to the substance. It is most 
usually reddish, because the gas holds in so- 
lution a little charcoal. A redhot iron likewise 
sets lire to hydrogen gas. From my expe- 
riments it follow s, that the temperature at 
w hich the gas takes fire is about 1000°. 
If pure oxygen and hydrogen gas be mixed 
together, they remain unaltered; but if a. 
lighted taper he brought into contact with 
them, or an electric spark be made to pass-- 
through them, they burn with astonishing ra- 
pidity, and produce a violent explosion. If . 
these two gases be- mixed in the proportion- 
of one part in bulk of oxygen gas and 2.527 
parts of hydrogen gass, or, more accurately, . 
85 parts by weight of oxygen gas and 15 of< 
hydrogen gas, they explode over water with- 
out leaving. any- visible residuum ; -the vessel - 
in which they were contained (provided the 
gases were pure) being completely filled with* 
water. But if the explosion be made in a- 
close vessel, there is always found instead of 
them a. quantity, of. water exactly equal to 
them in weight This water must be com- 
posed of these two gases; for it did not pre- 
viously exist in the vessel, and no. other sub- 
stance besides the gases were introduced. 
Water then is composed of oxygen and hy- 
drogen; and the combustion of hydrogen is 
nothing else but the act of its combination . 
with oxygen. 
When two parts (in bulk) of hydrogen gas 
are mixed with six parte of common air, the 
mixture explodes with equal violence; and 
after tire explosion, the bulk of the mixture Is 
reduced to rive parts. The whole of- the hy- 
drogen gas is consumed, and likewise all that* 
part of the common- air Which consists of ox- 
ygen gas, and there is formed a quantity of. 
water: equal in weight to these two bodies,* 
This experiment is often employed to ascer- 
tain the purity of hydrogen gas. Common, 
air and the hydrogen gas to be examined are 
mixed in certain proportions in a glass tube, 
graduated and closed at one end ; they are 
then tired by an electric spark. The purity 
of tile gas is proportional to the diminution of 
bulk. 'Thus, when the bulk of a mixture of. 
two parts of hydrogen gas and six parts of air 
is diminished after the explosion to five parts, . 
the hydrogen gas may be considered as pur eg ; 
if only to six, it contains some foreign ingre- 
dients, and so on. This method of detecting 
the purity ot hydrogen gas was first employed 
by Berthollet. Volta, indeed, had employed' 
it before him; but for a different purpose. 
Hydrogen gas is not sensibly absorbed by 
water, though left for .sbme time in contact; 
with it. But by artificial pressure water may 
be made to absorb about the third part of its 
bulk of that gas. . The taste of the water rs 
not sensibly altered . Mr. Paul, who first 
formed this compound, informs us, that it ids 
1 . 
