MONTHLY 
WeLunit, Nos | 
“MA 
TULY- Leon 
GAZINE 
eee eee aes 
[Price 1s. 6d. 
ORIGINAL 
For the Monthly Magazine. 
An account of the IMPROVEMENTS of 
the PORT of LONDON, and more parti- 
cularly of the tutended BRIDGE, confijt- 
ing of a fiugle ARCH of 600 FEST 
SPAN- . 
OTHING tends fo much to pro- 
mote the improvements of a ftate, 
as the eftablifhing of an ealy and uninter- 
rupted cormmunication through alli its dif- 
tridis; it has therefore always ‘been a 
leading object with. every well-wither of 
his country, to render the general inter- 
éourfe as perfeé&t and convenient as poffi- 
ble: public roads and bridges have’ been 
the means chiefly employed to eltablifh 
this intercourfe: bridges, as requiring ’ 
fcientific and mechanical knowledge, and 
in many cafes, the utmott exertions of 
talents and fkill, have frequently engaged 
the attention of perfuns of eminence and 
jJearning. 
It would be an amufing tafk to trace 
the progrefs of this ufeful art from the 
rude efforts of the favage in his unaffifted 
ftate, to the magnificent works of civi- 
lized nations, when fcience, wealth, and 
increafing population, have united to 
overcome difficulties confidered betore as 
unfurmountable. 
When a work is to be performed, man- 
kind at Arlt muke ule of the materials 
which are neareft at hand, and- require the 
Jeaft {kill in. the preparation: timber and 
ftone were therefore the materials with 
which bridges were firft conftructed ; and 
thofe edifices have been rendered more or 
lefs perfeét, in proportion to the quality 
of the materials, the fate of the arts, and 
the degree of wealth and power, in the 
countries in-which they were erected. 
In our clde bridges, it is evident, 
there has been much timidity, and only a 
fmall portion of fkili; in deep-water, the 
lower parts of the piers have been con- 
ftruGted of timber, and the mafonry be- 
gins to take place at the line of low-wa- 
ter ;—the arches are of narrow f{pan, and 
the mafonry employed in them is tre- 
quently compofed partly of rubble, and. 
partly of {quared ftones ;—in time, means 
were deviled (by ufing coffer-dams. and 
caiffoons) to place the maionry as low, 
commonly lower, than the naturai bed of 
the river; the arches were alfo formed of 
“Montrurx Mac, No. 74, 
COMMUNICATIONS. 
a bolder fpan, and the mafonry was made 
much more perfeét; being all of fquared 
ftone, In this manner, bridges have been 
conftructed in Italy, France, and the 
Britith Ifles, which have juftly been con- 
fidered, not only as works of general uti- 
lity, but of great magnificence. 
In like manner, timber-bridges have- 
been gradually improved, from the rough 
trunk of a tree thrown acrofs a {mall 
ftream, to the bold and ingenious labours 
of the Swifs carpenter at Schaff haufen. 
Bridgeés continued to be chiefly com- 
pofed of timber or of ftone, till of late 
years, of account of economy, in fome 
cafes they have been built with bricks. 
Metals, not being found in a pure ftate, 
require much labour and expence to make 
them fubfervient to the parpofes of man, 
and therefore in the uncultivated periods 
of focicty were not applied to works of 
great magnitude; but the important im»? 
provements in chymical and  mecha- 
nical knowledge have in’ a great de- 
gree removed thofe difficulties, and ren- 
dered them not only the mo powerful but 
the moft ufeful means of man. 
Tron being the moft abundant, chean, 
and generally ufeful of all thé metale, has, 
of late years, been applied in all works 
where great ftrength was required in prow 
portion to the weieht of the material ; 
herfce cylinders, beanis, and pumps for — 
fieam-engines, boats* and barges for 
canals and navigable rivers, beams+ and 
pillars for daree buildings, and bridges 
have been conftructed of iron. 
The firtt iron-bridge we know of, is 
over the rivet Severn, near Coalbrooke- 
Dale, in Shropthire; it confifts of an arch 
100 feet and 6 inches in the fpan, and 
rifes 45 feet; there are five ribs, each caft 
in two pieces, fecured, where they join at 
the crown of the arch, by acaft-iroa key- 
plate, and connected together horizontally 
SRONGLEEE et NT EOI, 
* Mr. John Wilkinfon has contructed boats 
and barges of iron, fome of which are ufed on 
the River Severn, and the others upon the 
canals in Staffordfhire and Worcefterfhire, » 
T A large manufaory for {pinning flax into 
thread, by machinery worked by aiteam-en- 
gine, has been eredted at Shrewlbury, by Mr., 
Baze, where there are four heights of foors and 
a roof, compofed of brick arches which are.\ 
fupoorted by caft-iron beams aad pillars. 
au. and 
