$74 Mr Macl arenas Account of the Ancient Canal 
upon as many dial-plates divided into ten divisions each, and 
numbered, any quantity of fluid which may have passed as far 
as 100,000,000 cubic feet, without any attendance, or the pos- 
sibility of committing an error ; n is a check-spring acting on the 
teech of the ratchet wheel m. 
The tumbler, f consists of a wooden bar, mounted upon an 
axis in its centre ; it turns up at each end, and two iron-rods, 
o o, are passed through the ends, and secured by screws and 
nuts : these rods serve as guides to conduct a cast-iron ball, 
from pne end of the tumbler to the other alternately ; and which 
ball strikes and rests against leather pads or cushions, which 
are provided at each end of the tumbler to receive it. On the 
under side of the tumbler are two blocks, r r, against which the 
studs e e , on the stems of the float, act ; and when either end of 
the tumbler is raised to the position shewn by the dotted lines 
s s , the ball suddenly runs down, and, by its momentum, strikes 
upon one of the ends of a lever, t , turning upon an axis in its 
centre, and from each end of which rods descend, to which the 
conical valves are hung, and thus suddenly opens one valve and 
shuts the other ; at the same time assuming the position shewn 
at v v. There are two cast-iron blocks, u u, fixed underneath 
the tumbler, to strike upon the ends of the lever, t. Gaps are 
made in the inner edges of the copper-floats, to permit the rods 
of the valves to pass freely by them. The whole machine is 
surrounded and inclosed in a proper manner, and strengthened 
by framing, which need not, however, be particularly de- 
scribed here. 
Art. X.— Account of the Ancient Canal from the Nile to the 
Red Sea. By Charles . Maclauen, Esq. With a Map 
and Section. 
On a first view, no scheme would appear more impracticable, 
than that of cutting a navigable canal through a desert nearly a 
hundred miles in breadth, in which there is not a single brook 
or rivulet, and scarcely even a drop of fresh water to allay the 
thirst of the traveller. Yet it is certain that the project must 
not only have been practicable, but easy, since it was accom- 
