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courfe of time, becaufe the water only depofits the ftony 
matter from the attraction of the iron, which being once 
covered with a flight thicknefs, the water has no longer 
accefs to the iron. We have heard of an expedient of 
putting lime into the water, when it was found that the 
water was fo corrofive as to become tinged by running 
through iron pipes newly laid down. A rapid current of 
this lime-water being caufed through the whole length 
fora few days, the pipes become coated with the calca¬ 
reous matter. At firft, after this, the frefli water tailed of 
lime, but it became pure in a (hort time, becaufe, in the 
firfl inftance, more lime was depofited than could be 
combined with the oxydated furface of the iron, and this 
excefs would of courfe be carried away again by the frefli 
water, but no more. 
Stone Pipes. —The prejudice which the public at firft 
entertained againlt iron pipes, induced many projeClors 
to find out other fubllances, which would have the 
ftrength and durability of metal. Sir George Wright 
propofed Hone, and invented a machine for cutting out 
cones from the hollow of the pipe. He firft employs a 
boring or drilling machine, to pierce a fmall hole through 
the centre of the block of ftone, in the axis of the in¬ 
tended pipe. Another machine is then ufed, confiding 
of a faw applied in a frame, which revolves on a round 
iron rod, palled through the central hole previoufly 
drilled : the frame gives the means of fixing the faw at 
any required diftanpe from the rod, and attaching it 
firmly thereto at each end : its edge will of courfe, when 
turned round, defcribe the furface of a cylinder, of the 
diameter of the intended pipe. The faw and central rod 
are rather longer than the block of ftone, which permits 
them to be moved backwards and forwards endways, to 
give the motion of flawing with fand and water in the 
ufual manner. In their operation, the block of ftone is 
placed witli the rod horizontal; the flaw is entered at 
another hole, previoufly drilled through the ftone ; and, 
as the law cuts, the central rod guides it round on a 
centre, till it feparates the core all round, and this being 
taken out, leaves a pipe or tube. Sir George obtained a 
patent for this invention in 1805; and it was praftifed 
lor fome time, and many large ftone pipes were laid ; but 
great difficulties arofe in making good joints; they were 
attempted by Roman cement, which adhered fo well, as 
to make them perfebl, if the pipes were well bedded ; but 
the continual tremor of heavy carriages palling over them 
foon difturbed many joints, and broke the bond of the 
cement. Mr. Samuel Hill took out a patent, in 1810, for 
uniting thefe pipes together at every joint by a collar of 
ftone, into which the extremities of two pipes are made 
to fit, fo that about two inches of each flhal 1 enter it, and 
reach to its centre, where they are to meet. A fufficient 
quantity of cement is to be fpread on the ends of each 
pipe, and in the internal part of the collar, before they 
are infertedinto it, to prevent water from palling through 
the joints. Although this obviates one difficulty, ftill 
the expenfe of ftone pipes is prodigious; at lead in 
London, where the price of materials alone, without any 
coft of workmanlhip, would be too great. In fituations 
where that material is plentiful, they may be ufed, and 
the labour of making them will be reduced very low by 
a machine invented by Mr. Murdoch, and for which he 
had a patent in 1810: it is very fuperior to the above, 
which is only applicable to large pipes; befides, the 
trouble of previoufly drilling two (mall holes the whole 
length of the pipe is wholly laved. 
Copper Pipes are too expenfive to be employed, except 
in particular fituations. They are made of copper plate 
turned up and foldered, and are much ufed in diftillers’ 
work, becaufe they can be tinned withinlide, and then 
communicate no tair.t to what pafles through them. 
Lead Pipes are univerfally employed for all fmall water- 
pipes, chiefly from the facility of bending them in any 
dire£lion and floldering their joints. Although fome 
kinds of water corrode the metal by degrees, this will 
P E. 
not produce fo much harm as iron under the fame cir- 
cumftances, but would be a molt dangerous poifon if it 
was ufed in fufficient quantities to have any eft'edl at all. 
The greateft proportion of the leaden pipes ufed in water¬ 
works, was, till of late years, made of fheet-lead wrapped 
round an iron or wooden core, and the joint foldered up. 
The expenfe and trouble of this method was confiderable, 
and the pipes thus made extremely liable to burft at the 
joint, particularly if bent with a fudden angle. Thefe 
defeds fuggefted the idea of calling the lead in the form 
of pipes, by which means the trouble of previoufly calling 
and laminating the lead into Iheets would be fpared, and 
alfo the uncertainty of the foldered joints. Such pipes 
are call in an iron mould, made in two halves, forming, 
when put together, a hollow cylinder, of the fize of the 
intended pipe. A core, or iron rod, the fize of the bore 
of the pipe, is adapted to this hollow mould when the 
halves are put together, and fecured by fcrews or wedges, 
fo that it exadly occupies the centre of the hollow mould, 
leaving therefore an equal fpaceall round between them. 
A fpout, or entry for the admiffion of the melted lead, is 
made by a correfponding notch cut in each half of the 
mould, and at another place is a fimilar vent for the 
efcape of the air. This mould is fixed down upon a long 
bench ; and a rack, moved by toothed wheels and pi¬ 
nions, is fitted up at one end of it, in a line with the 
centre of the mould. A hook at the end of the rack, 
being put into an eye at the end of the core of the mould, 
affords the means of drawing out the core, when the pipe 
is caft round it by pouring the melted lead into the 
mould, with the core in it: when the Ipad is cold, the 
core is drawn out very nearly to the end of the pipe, by 
the rack and wheel-work before mentioned. The halves 
of the mould are then feparated, and the pipe moved 
along in the mould, fo that only an inch or two of its 
end remains in the mould, the halves of which are again 
fattened together with the core between them, and its 
end entered an inch or two into the firft piece of pipe. 
The mould is now filled with melted lead, the heat of 
which fufes and unites it with the end of the firft piece, 
fo as to double its length. The core is again drawn out 
a fecond time, and another length caft to the former. 
This method produces pipes of any length in one piece, but 
they are liable to have air-bubbles in them, which produce 
holes when the metal is thin ; and the joinings of the dif¬ 
ferent lengths are not always perfeblly found. 
The method which is now very generally adopted, is 
to caft the lead in an iron mould, upon a cylindrical iron 
rod of the fize for the bore of the intended pipe, the lead 
being three or four times the thicknefs of the intended 
pipe, and in ffiort lengths, which are then drawn through 
holes in pieces of fteel, in the manner of wire-drawing, 
till the pipe is reduced to the intended thicknefs, and 
drawn out to the proper length. Another method is to 
reduce the pipe by repeatedly palling it through the two 
rollers of a flatting-mill, in each of which a number of 
femi-circularnotches are formed all round, fo that the two 
rollers, when put together, have a number of circular 
cavities between them, which gradually diminifli in dia¬ 
meter from one end of the rollers to the other. The 
pipe is firft rolled between the largeft of thefe cavities, 
then in a fmaller, and fo on to the laft, which extends the 
pipe to its proper length, and diminiflies its fubllance to 
the proper thicknefs, at the fame time by condenfing the 
metal hardens it, and makes a very ltrong tube witli very 
little metal. Mr. John Wilkinfon of Brolely, the celebra¬ 
ted iron-manufadlurer, took out a patent, in 1790, for 
the laft mentioned method, which he prablifed op a very 
extenfive fcale : he was not, however, the original in¬ 
ventor, the fame thing having been propofed, in 1728, 
by M. Fayolle; (fee “ Machines Approuves par l’Aca- 
demie Royale,” vol. v. p. 50.) Since the expiration of 
the patent, many manufactories of this article have been 
eftabliflied, fome employing rollers, and others the draw- 
bench, for extending the pipes. 
2 
We 
