MECHANICS. 
The other end of the lever, L, is long enough to reach 
to the uprights, and has there a fmall rope, extended 
from the end of it up to the inclined planes, fo that the 
follower, when drawn up to the higheli, draws this rope, 
• nd raifes the long end, L, of the lever, deprefling the 
other, and the forcing bar 5. By the horfes going round, 
the great rope, H, is wound about the drum C, and the 
rant is drawn up by the tongs in the follower, till they 
come between the inclined planes, which, by fliutting the 
tongs at the top, open them below, and fo difcharge the 
ram, which falls down between the uprights upon the 
pile, as noticed before. Immediately after the ram is dif- 
charged, a piece upon the follower takes hold of the rope, 
which raifes the end L of the lever L N, and caufes its end 
N to defcend, and prefs down the forcing-bar, 5, upon 
the little lever, 3, which, by drawing down the holt Y, 
unlocks the drum, C, from the great wheel B ; and then 
the follower, being at liberty, comes down by its own 
weight to the ram 5 and the lower ends of the tongs flip 
over the eye of the ram, the weight of their heads caufing 
them to fall outwards, and fallen upon it ; then the 
weight, 4, pulhes up the bolt, Y, into the drum, which 
locks it to the great wheel, and fo the ram is drawn up 
as before. As the follower comes down, it caufes the 
drum C to turn backward, and unwinds the rope from 
it, while the horfes, the great wheel, pinion, and fly, go 
on with an uninterrupted motion ; and, as the drum is 
turning backward, the counterpoife is drawn up by its 
rope, T, winding upon the fpiral fufee D. 
There are feveral holes in the under fide of the drum, 
and the bolt Y always takes the firft that it finds, 
when the drum Hops by the falling of the follower upon 
the ram, till which ftoppage the bolt has not time to flip 
into any of the holes. But the fame effeft is more cer¬ 
tainly produced by a crooked lever, t, fig. 67, fixed on 
the framing Z, over the end of the vertical fliaft; one end 
of this has a roller, which is prefled upon by the great 
roge II, the other end holds down the catch, 5, of the 
forcing-bar ; but, as foon as the great rope flackens, it 
retires, and gives liberty to the fmall lever, 3, to pufli up 
the bolt. As long as the great rope has a tenfion upon 
it, to fupport the weight of the ram or follower, the 
crooked lever is kept in clofe contact with the forcing- 
bar ; and, when that is deprefled, (todifcharge the bolt Y,) 
by locking over its catch 5, the crooked lever keeps it 
down, till the follower touches the ram ; the great rope 
then flackens, and the fpring v H difcharges the crooked 
lever from the catch of the forcing-bar, and gives liberty 
to the fmall lever, 4, to pufh up the great bolt, and to 
lock the drum to the great wheel; and.the ram is drawn 
up again as before. 
The peculiar advantages of this engine are, that the 
weight of the ram, or hammer, may be raifed with the 
force of horfes inllead of men ; that, when it is raifed 
to a proper height, it readily difengages itfelf, and falls 
with the utmolt freedom ; that the forceps or tongs are 
lowered down fpeedily, and inrtantly of themfelves again 
lay hold of the ram, and lift it up ; on which account 
this machine will drive the greateft number of piles in 
the leaft time, and with the fewell labourers. 
The theory of Mr. Valoue’s engine depends on the fol¬ 
lowing principles, viz. 
1. If the reliftance of the ground and the mafles of the 
piles be equal, the depths to which they will be driven 
with a fingle blow will be as the produft of the weight of 
the ram into the height through which it falls. 
a. If the mafles of the ram and heights through which 
it falls are both equal, the depths to which the piles will 
be driven will be in the inverl'e ratios of the mafles of the 
piles into the fuperficies of that part of them which is al¬ 
ready immerfed in the earth. 
3. If all thefe things be unequal, the depths will be in 
a ratio compounded of the direct ratio of the heights 
through which the ram falls into its mafs, and the inverfe 
VOL. XIV. No. 1006. 
697 
ratio of the mafs of the pile into its immerfed fuperfi¬ 
cies. 
4. If the weights of the ram be equal, and alfo the 
weights of the piles, the depths to which they will be 
driven will be as the heights through which the ram falls 
direftly, and the imrnerled fuperficies oi the piles. Or, 
becaufe the immerfed fuperficies of the piles are as the 
depths through which they are already driven into the 
earth, thefe depths are (imply as the fquare-roots of the 
heights through which the ram falls. 
Thefe principles are founded on the general fuppofition 
that the fpace through which the weight falls is eltimated 
by the product of its mafs into the fquare of its velocity, 
or into the height through which it falls. 
Hence it is inferred, that the difiance through which a 
pile will be driven by each fucceeding blow will be lefs 
and lefs, as the fuperficies of that part of the pile which 
is immerfed in the ground increafes; and, confequently, 
that there is a certain depth, beyond which a pile of a 
given mafs and fcantling carmot be driven; the mafs of 
the ram and the height through which it falls at firft be¬ 
ing afiigned. It appears alfo, that the loading the pile 
with weights, and thereby increafing its mafs, will be fo 
far from accelerating its del'cent, that it will abfolutely re¬ 
tard it. See fome curious obfervations on the ftrufture 
and operation of this engine by Mr. Bugge, profelfor of 
aftronomy and mathematics in the academy of Copenha¬ 
gen, &c. in the Phil. Tranf. for 1779- vol. lxix. part i. 
art. 1 z. 
The piles at Weftminfter-bridge, when driven by the 
above machine till they were quite firm, were cut off, un¬ 
der water, by a machine, to be level with the furface of 
the ground to found the piers upon. This machine con¬ 
fided of a framing which was adapted to fit upon the up¬ 
per part of the pile, and could be fixed faft thereto. Tha 
lower part of this frame formed guides for the faw, which 
reciprocated horizontally at a certain depth beneath the 
top of the pile, and had weights to caufe it to advance up 
to the cut. The faw was put in motion by ropes from 
each end, which were conducted, over proper pulleys, to 
two men Handing on a float or raft at the furface. After 
fixing the machine, before the fawing was begun, the 
whole machine was fufpended by a tackle, which there¬ 
fore took up the top part of the pile with the machine as 
foon as it was cut off. This was the invention of Mr. 
Etheridge, carpenter to the works at Weftminfter-bridge.'f 
it was very effeftive, as the time employed in cutting off 
a fir-pile of fourteen or fixteen inches fquare, in ten feet 
depth of water, was feldom more, and often lefs, than a 
minute and a half. A machine, more convenient than 
this in its application, and not lefs effeftive, has been 
fince invented by Mr. Foulds, to whom the Society of 
Arts prelented a gold medal for the invention in the year 
1795. A A B, fig. 68. is the external frame, confiding of 
four parallel rails A, framed into two others, B, at right 
angles, with proper crofs-pieces to unite them, and in¬ 
clined to ftrengthen the whole. Within this frame a fe- 
cond or internal frame, D E, is fituated 5 like the other, 
it has four parallel pieces, D and E, connefted together 
into one frame by crofs pieces; at the top it has two 
pieces a, a, which reft upon the beam B, and fofpend its 
weight, and on thefe it is capable of Aiding backwards 
and forwards between B B, always preferving its paral- 
leliftn, becaufe it is moved by the racks, d, d, affixed to 
it, one at top, and the other at the bottom ; the pinions 
for both are fixed on a vertical axis e, fupported in the 
external frame ; therefore, by turning the handle r, the 
internal frame with the faw is advanced to the pile, as at K, 
fig. 70. The faw itfelf is fuftained in a frame L, fig. 69, 
which fits, in the manner of a fath-frame, between the two 
beams, D, of the internal frame, and has racks, ff, (dot¬ 
ted) behind it, which work in pinions on an axis g, fig. 70, 
extended acrofs the frame; and by the handle, y, of this, 
it,is capable of being drawn up and let down, or detained'' 
% P af 
