447 
Patents, 
medes* Screw, thence named the Egyptian Pump ; but they now 
generally use Wheels (Wallowers) which carry a rope or chain 
of earthen pots, holding about 7 or 8 quarts a piece, and draw the 
water from the canals. There are besides, a vast number of wells 
in Egypt, from which the water is drawn iiii the same manner to 
water the gardens and fruit trees ; so that it is no exaggeration to 
say, that there are in Egypt above 200,000 oxen daily employed 
in this labour.” Shaw’s name of Pei'sian wheel has been since giv*- 
en more particularly to a wheel with buckets, either fixed or sus- 
pended on pins at its periphery. — Mortimer’s Husbandry, 1, 18, 
Duhamel, V. Ferguson’s Mechanics, plate 13. But his figure, 
and the verbal description of the Universal History, prove, that 
the string of buckets is meant under that name. His figure differs 
from Evans’ construction in the circumstances of the buckets be- 
ing round, and strung through their bottom on a chain ; but it is 
the principle ; to wit, a string of buckets, which constitutes the 
invention, not the form of the buckets, round, square, or hexagon j 
nor the manner of attaching them, nor the material of the connect- 
ing band, whether chain, rope or leather. Vitruvius, L. X. c. 9, 
describes this machinery as a windlass, on which is a chain descend- 
ing to the water, with vessels of copper attached to it ; the windlass 
being turned, the chain moving on it will raise the vessels, which 
in passing over the windlass, will empty the water they have brought 
up into a reservoir : and Perrault, in his edition of Vitruvius, Pa- 
ris, 1784, folio, plates, 61, 62, gives us three forms of these water 
elevators, in one of which the buckets are square, as Mr. Evans* 
arc. Bossut, Histoire des Mathematiques, I. 86, says, “ The 
drum wheel, the wheel with buckets, and the chafielets^ are hydrau- 
lic machines, which come to us from the ancients ; but we are igno- 
rant of the time when they began to be put into use.” The cha- 
pelets are the revolving band of buckets, which Shaw calls the 
Persian wheel, the moderns a chain pump, and Mr. Evans eleva- 
tors. The next of my books, in which I find these elevators, is 
Wolf’s Coursde Mathematiques, I. 370, and plate 1, Paris, 1747— 
8 VO. Here are two forms ; in one of them the buckets are square, 
attached to two chains, passing over a cylinder or wallower at top, 
and under another at bottom, by wdiich they are made to revolve. 
It is a nearly exact representation of Evans’ elevators. But a more 
exact one is to be seen in Desagulier’s Experimental Philosophy, 
II. plate 34. In the Encyclopedic de Diderot et D’Alembert, 8vo. 
edition dq, I^aiisanne, 1st voL of plates, in the four subscribed “ 
