3SS IRK 
portable machine: an implement 'to him not lefs ufeful 
than a fpade to an European peafant. The fabrication of 
thole machines gives employment to a great number of 
artificers. 
To apply the fyflem of irrigation to thofe plantations 
which were on a Tandy foil far elevated above the river, 
it was neceifary to raife the water to heights which could 
not be attained by the means hitherto mentioned to be 
praftifed by the Chinele. But the want fuggefted the re¬ 
source ; and a machine was invented by them, as inge¬ 
nious in its contrivance, as it was cheap in its materials, 
eafy in its operation, and effectual to its purpofe. This 
is fhown at fig. 2. Two hard-wood polts or uprights, 
R R, are firmly fixed in the bed of the river, in a line 
perpendicular to its bank. Thefe polls fupport the axis, 
C, about ten feet in length, of a large and durable wheel, 
confifting of two unequal rims, the diameter of one of 
which, A, clofeft to the bank, being about fifteen inches 
fhorter than that of the outer rim, B ; but both dipping 
in the dream, while the oppofite fegment of the wheel 
rifes above the elevated bank. This double wheel is con- 
nefted with the axis, and is lupported by fixteen or eigh¬ 
teen fpokes, DDDD, obliquely inferted near each extre¬ 
mity of the axis, and eroding each other at F F, about 
two-thirds of their length. They are there llrengthened 
by a concentric circle, and fattened afterwards to the 
rims: the fpokes inferted in the interior extremity of the 
axis, reaching the outer rim, and thofe proceeding from 
the exterior extremity of the fame axis, reaching the inner 
and fmaller rim. Between the rims and the erodings of 
the fpokes, is woven a kind of clofe balket-work, H, 
ferving as ladle-boards or fioats, which, meeting fuccedive- 
ly the current of the dream, obey its impulfe, and turn 
round the wheel. To both its rims are attached fmall 
tubes or fpouts of wood, L, with an inclination of about 
twenty-five degrees to the horizon, or to the axis of the 
wheel. The tubes are clofed at their outer extremity, and 
open at the oppofite end, M. By this pofition, the tubes 
which happen in the motion of the wheel to be in the 
llream with their mouths or open ends uppermoft, fill 
with water. As that fegment of the wheel rifes, the 
mouths of the tubes attached to it alter their relative in¬ 
clination, but not fo much as to let their contents flow 
out, till fuch fegment of the wheel becomes the top. The 
mouths of thofe tubes are then relatively deprefied, and 
pour the water into a wide trough, O, placed on polls, 
from whence it is conveyed as may be wanted by the long 
pipes, or tubes, P. The only materials employed in the 
conftruftion of this water-wheel, except the nave or axis, 
and the polls, S S, on which its refts, are afforded by the 
bamboo. The rims, the fpokes, the ladle-boards or floats, 
and the tubes or fpouts, and even the cords, are made of 
entire lengths, or lingle joints, or large pieces, or thin 
fiices, of the bamboo. Neither nails, Springs, ferews, or 
any kind of metal, enters into its conftruflion. The parts 
are bound together firmly by cordage, all'o of flit bamboo. 
Thus, at a very trifling expence, is conftrufted a machine 
which, without labour or attendance, will furnilh, from a 
conliderable depth, a refervoir with a conftant fupply of 
water adequate to every agricultural purpofe. 
Thefe wheels are from twenty to forty feet in diameter, 
according to the height of the bank, and confequent ele¬ 
vation to which the water is to be raifed. A wheel of 
thirty feet is capable of fullaining with eafe twenty tubes 
or fpouts, of the\ ength of four feet, and diameter two 
inches in the clear. The contents of fuch a tube would 
be equal to fix-tenths of a gallon, and a periphery of 
twenty tubes twelve gallons. A llream of a moderate 
velocity would be fufficient to turn the wheel at the rate 
of four revolutions in one minute, by which would be 
lifted forty-eight gallons of water in that fliort period; in 
one hour, two thoufand eight hundred and eighty gallons; 
and fixty-nine thoufand one hundred and twenty gallons, 
or upwards of three hundred tons of water, in one day. 
This wheel is thought to exceed, in molt refpefls, any 
IRK 
machine yet in ufe for fimilar purpofes. Tile Perfiaa 
wheel, with loofe buckets fufpended to the edges of the 
rim or fellies of the wheel, fo common in the fouth of 
France and in the Tyrol, approaches neareft to the Chi- 
nefe wheel; but is vallly more expenfive, and lefs Ample 
in its conltrudlion, as well as lefs ingenious in the con¬ 
trivance. In the Tyrol, there are alio wheels for lifting 
water, with a circumference of wood hollowed into fcoops; 
but they are much inferior either to the Perftan or Chinefc 
wheel. Staunton's EmbaJJy , vol. ii. 
IRRIG'UOUS, adj. Watery; watered: 
The flow’ry lap 
Of fome irriguous valley Spreads her llore. Milton. 
Dewy; moill. Phillips feems to have miftaken the Latin 
phrafe irruguus fop or: 
Ralh Elepenor 
Dry’d an immeafurable bowl, and thought 
T’ exhale his furfeit by irriguous fleep : 
Imprudent! him death's iron fleep opprell. Phillips. 
IRRIS'ION, f. [irri/io, Lat. irrifion, Fr.] The a< 5 l of 
laughing at another.—Ham, by his indifereet and unna¬ 
tural irrifion, and expofing of his father, incurs his curfe. 
Woodward. 
IRRITABIL'ITY,yi [irritare, Lat.] In anatomy and 
medicine, a term firfl invented by Glilfon, and adopted, 
by Dr. Haller, to denote an elfential property of all animal 
bodies; and which, he fays, exifts independently of, and 
in contradiflin&ion to, fenfibility. This ingenious author 
calls that part of the human body irritable, which becomes 
fhorter upon being touched ; very irritable, if it contrails 
upon a flight touch ; and the contrary, if by a violent 
touch it contrafls but little. He calls that a fenfible part 
of the human body, which upon being touched tranfmits 
the impreflion of it to the foul; and, in brutes, he calls 
thofe parts fenfible, the irritation of which occafions evi¬ 
dent figns of pain and difquiet in the animal. On the 
contrary, he calls that infenfible, which, being burnt, torn, 
pricked, or cut till it is quite deftroyed, occafions no fign 
of pain nor convulfion, nor any fort of change in the 
fituation of the body. From the refult of many cruel ex¬ 
periments he concludes, that the epidermis is infenfible ; 
that the fkin is fenfible in a greater degree than any other 
part of the body; that the fat and cellular membrane are 
infenfible ; and the mufcular flefh fenfible, the fenfibility 
of which he aferibes rather to the nerves than to the flefh 
itfelf. The tendons, he fays, having no nerves diftributed 
to them, are infenfible. The ligaments and capfulx of the 
articulations are alfo concluded to be infenfible; whence 
Dr. Haller infers, that the fharp pains of the gout are not 
feated in the capfulas of the joint, but in the fkin, and in 
the nerves which creep upon its external furface. The 
bones are all infenfible, fays Dr. Haller, except the teeth; 
and likewife the marrow. Under his experiments, the pe- 
riofteum and pericranium, the dura and pia mater, ap¬ 
peared infenfible ; and he infers, that the fenfibility of the 
nerves is owing to the medulla, and not to the membranes. 
The arteries and veins are held fufceptible of little or no 
fenfation, except the carotid, the lingual, temporal, pha- 
ryngal, labial, thyroidal, and the aorta near the heart; 
the fenfibility of which is aferibed to the nerves that ac¬ 
company them. Senfibility is allowed to the internal mem¬ 
brane of the flomach, inteftines, bladder, ureters, vagina, 
and womb, on account of their being of the fame nature 
with the fkin : the heart is alfo admitted to be fenfible: 
but the lungs, liver, fpleen, and kidneys, are poflefled of 
a very imperfeft, if any, fenfation. The glands, having 
few nerves, are endowed with only an obtufe fenfation. 
Some fenfibility is allowed to the tunica choroidis arid the 
iris, though in a lefs degree than the retina; but none to 
the cornea. Dr. Haller concludes, in general, that the 
nerves alone are fenfible of themfelves; and that, in pro¬ 
portion to the number of nerves apparently diftributed to 
particular parts, fuch parts poflefs a greater or lefs degree 
of fenfibility. 
Irritability, 
