396 B R I 
ers. G, fig. 9, (hews the planks lying over the bearers, 
and fecured to them by crofs iron plates : the plates are to 
be let into the furface of the planks next the joints, that 
one half the width of the plate may be on one plank, and 
the other half on the other, with bolts palTing through the 
fame, to fecure the planks to the bearers : on thefe planks 
gravel and ballad may or may not be laid. H, fig. 9, re- 
prefents one of the crofs timbers in the crown of the fuf-' 
pending ribs. Thefe are to be continued down as low as 
the headway for waggons will admit, and are to have crofs 
and diagonal timbers framed in between them, to prevent 
any lateral preffure from injuring the ribs: they are to be 
connected to the ribs by proper bearings, bolts, &c. I, 
fig. 9, fh.ews a footway, which may or may not be affixed 
to the bridge at its building, or which may be affixed at 
any future time, it confilfs, according to this fedion, of 
wrought-iron bottom bars, fide bars, and large and (mail 
brace bars : one of each is to be affixed to every fuf- 
pe'ndmg bar, by the bottom bar palling on the top of the 
horizontal rib, and turning up to receive a wroughf-iron 
bar, which is to fecure it to the fufpending bar, as (hewn 
at K. When a footway is intended to be ereded, the caff- 
iron plate of the horizontal rib (hould be wider than the 
timbers, to leave a fufficiency of it for the fide and brace 
bars to bear thereon ; the fide bars may be fecured to tfie 
rib by (tuples. Four or more timber-bearers are to lie 
longitudinally over, and are to be notched on to the bot¬ 
tom bars: on thefe bearers are to be laid planks, which 
are to crofs the bearers, and to form the floor; and on or 
againff the front of the outermoft bearer, are to be fixed 
polls, fecured by the iron braces, and alfo at the bottom 
to the bars: to thefe polls proper rails, and pannels filled 
in, may be affixed. The top of the butirefl'es may be 
formed into a double parapet, for a footway between, or 
the paffengers may turn off into the carriage-way, - 
Fig. 10, reprefents part of a bridge on the above-de- 
feribed conftrudion, in which a draw-bridge is introduced. 
A A, are the parts of the bridge to be drawn up. B B, 
is an iron frame, fecured to the circular rib, and to two 
fufpending bars, for the purpofe of diftributing the weight 
to, and preferving the form of, the arch. The chains here 
fhewn are of the kind generally ufed, but fuch as are more 
proper are on the principle of thofe for which the Society 
for the Encouragement of Arts and Munufadures have 
given a premium, and which aft in the fame manner as a 
rope. (See the article Chain.) C C, are iron rolling- 
wheels, on which the chains for railing the bridge are to 
pafs, (other rollers being on the infide,) and are fo placed 
as to caufe the bridge in fifing to clear the fufpending 
chains out of the way of the malls. The chains may ei¬ 
ther be palfed through the'rib at D, to wind up the bridge 
by a perpendicular direction, (in which cafe proper ma¬ 
chinery will be affixed on the bridgeway for that purpofe,) 
or the draw-bridge may be taken up by means of weights 
moving on the furface of the lower parts of the circular 
rib, and on fuch parts as may tend rather to benefit than 
to injure them ; and, as the weight of the draw-bridge will 
be progrellively let's on the chains, as it rifes, the increafed 
velocity and power of the weights maybe correded by the 
application of fprings and inclined planes. Various me¬ 
thods may be adopted for taking up and returning the 
draw-bridges with eafe and facility, and, by a connection 
of the chains, render the manual force neceffary to be em¬ 
ployed, not more than that of one perfon. As a counter¬ 
balance for the feparation of the bridgeway, (if only of 
one arch,) the ends of it are to go the farther on the but- 
trelfes, and are to be fallened to iron bars, brought up a 
confiderable way in the buttrelfes, and conneded with 
chain-bars laid horizontally in them, for the purpofe of 
forming additional binders to the horizontal ribs of the 
bridgeway. Where, from the great width of the river, 
more than one arch may be proper, this precaution will 
not be neceffary, as the horizontal rib will be continued to 
receive other additional fufpending ribs, as deferibed here¬ 
after in the confirmation of continued aqueduds. Fig. 11, 
D G E. 
reprefents the trunfverfe fedion of an aquedud to which 
the principles of my invention are applied. A, fig. 11, 
Ihews the horizontal rib, which is to be put together in a 
limilar manner to that deferibed for the bridge ; but, not 
being liable to fo much agitation, nor the fupport of fa 
great bearings, it may be of fmaller fcantlings. BB, are 
the circular fufpending gibs, compofed of call-iron, form¬ 
ed in the following manner: each rib piece is to be call of 
a proper length to break the heading joints, and may ap¬ 
pear folid on the face, or may be call of an open pattern, 
to give elegance to the appearance of the whole. One rib 
piece is to be laid and fecured to the other, fo that the rib 
may be of two; three, or more, pieces in width, on one fide 
of the fufpending iron, and of the fame number on the 
other fide ; and, when combined by bolts and ftraps, to 
conned them to each other, and for receiving the hang¬ 
ing irons, will form a double circular fufpending rib. This 
mode may be alfo applied to bridges, and that deferibed 
for bridges may be applied to aqueduds. C C, are the 
Appending irons, with heads of a fize fuflicient to cover 
the rib, and fecured at the bottom in the fame manner 
as deferibed for the bridgeway. The .heads are to be fe¬ 
cured to receires in tire top of the circular ribs, by proper 
bolts. D, is one of the girders, which may be put up 
and united as in the method propofed for the bridgeway. 
E, fhews one of the crofs flays, which, in this aquedud, 
to give it a light appearance, is propofed to be of cad or 
Wrought iron. Crofs .and diagonal irons are to be added, 
to anfwer the purpofe mentioned in the defcripti'on of the 
crown of the bridgeway. F, reprefent-- the horfe and foot 
path ; but, as the method of conltruding this path is near¬ 
ly the fame as that deferibed in the explanation of the foot¬ 
way to the bridge, no more need be obferved than that, 
this being affixed higher, the bottom and brace bars may 
be conneded to the fufpending irons by mortices and fmall 
bolts, and the door conliff of only,one thicknefs of bear¬ 
ers, laid longitudinally on the iron bottom bar. The bot¬ 
tom and (ides of this aque.lud mav be of wood, (lone, cad 
or wrought iron, wood lined with ffieet-lead, copper, or of 
other materials, having the upper parts filled inbv planks, 
to give them a bearing again!! the fufpending irons; by 
which means they will be prevented from any accident 
that a lateral preffure might otherwife occafion. For paf- 
fing boats and other veffels, an endlefs rope or chain is to 
be provided, and vertical and other rollers are to be fixed 
clear of the ends of the aqueduds : this rope or chain is to 
lie on the infide and ontfide of the fufpending irons, and 
round the rollers. When boats, &c. are brought up to 
the aquedud, they are to be made fall to that part of the 
rope or chain next them, and the force employed to draw 
them being taken to the other end of the path, and (aliened 
to that part of the rope or chain on theoutfideof the irons, 
by drawing towards the boats, &c. the firll of them will 
pafs the aquedud (the reft following) in the time the force 
applied is palling the pathway. This ltlethod of puffing 
boats, &c. may be avoided, by ereding the pathway on 
the infide of the bars, which may be high enough to per¬ 
mit the boats, &c. to pafs under it, fo that no extr.i-width 
in the aquedud will be neceffary on their account. An!, 
as the points of the fegments abut on each other, much 
of the precaution to be obferved in the conftrudion of a 
fingle arch, to prevent a longitudinal expanfion of the rib, 
will be rendered unneceffury, and the piers or fupports will 
not be liable to a lateral, but only to a perpendicular, pref¬ 
fure ; confequently they may be built mufeh ftpaller than if 
liable to a lateral preffure, and may be a frame-work of 
iron or other materials, if thought proper. By this me¬ 
thod bridges and aqueduds may be continued to any 
length, and extended to any width; they may be conti¬ 
nued, by placing fuch a number of ribs longitudinally as 
may be neceffary; and they may be extended, by adding, 
at fuch diftances as the weight and bearings may require, 
one, two, or more, ranges of ribs between the outer ones. 
The principles of my invention, as they are to be ap¬ 
plied to the covering-in of large buildings, may be uuder- 
(fcaod 
