344 HINTS TO THE PEOPLE OF INDIA— CAOUTCHOUC MANUFACTURE. 
METALLIC LIGHTHOUSES. 
Mr. Samuel Brown proposes employing 
bronze or cast-iron in the construction of light- 
houses, instead of stone. H e seems to ha ve made 
out that a bronze lighthouse would be incom- 
parably cheaper than a stone one, that it wotild 
be more secure against dilapidation or subver- 
sion by the waves, that tile lights would be 
better protected from the spray by which 
they are occasionally extinguished, that it 
could be erected in one-twentieth part of the 
time, and in situations where a stone structure 
is impracticable. It has been proposed to 
place a lighthouse on the Wolf Rock, near 
the Land’s-End, a position where it would be 
exposed to the most violent storms of the At- 
lantic : and a plan was drawn up for the pur- 
pose by Mr. Stevenson, who holds a high 
rank in this department of engineering ; which 
plan, Mr. Brown thinks, would require 15 
years for its execution, and cost 150,0001. Mr. 
Brown undertakes to erect one of bronze, 90 
feet high, which would answer the purpose as 
well as the stone one of 134 teet, for 15,000/. 
and to complete it in four months. — Scotswurt. 
LONGITUDE AT SEA. 
The Progress, a journal of Arras, states, that 
a person residing at Fauquembergue has, af- 
ter studying for thirty years, discovered the 
longitude at sea, and formed an instrument 
which constantly points out and rectifies the 
ship’s course, indicating the longitude and 
latitude in the chart. 
HISTORICAL RETROSPEC r OF 4 HE 
CAOUTCHOUC MANUFACTURE. 
( Continued from page 231.) 
Hitherto caoutchouc had been supplied 
entirely form the American continent ; but 
near tne close of the last, or the begining of 
the present century, it was discovered that 
several kinds of plants giowing in the East, 
tiiough very different in appearance from the 
hevea of Mexico, afforded the same substance, 
or one very much resembling it ; and hopes 
were again raised that extensive use might f)e 
made of the juice in its fluid state. Mr. Howi- 
son experimenteddiligently with it, and be-ides 
making gloves, shoes, &c., a process practised 
by the Indians of Para, he proceeded to 
saturate with it loosely woven fabrics, such as 
Cossembazar gloves and stockings: — 
“ Haying drawn them upon the wax 
moulds, 1 plunged them into vessels contain- 
ing the milk, which the cloth greedily absorb- 
ed. When taken out they w'eie so completely 
distended by the gum in solution, tliat, 
upon becoming dry by exposure to the air, 
not only every thiead, but every fibre of the 
cotton had its own distinct envelope, and in 
consequence was equally capable of resisting 
the action of fluid bodies as if of solid gum. 
“ This mode of giving cloth as a basis I 
found to be a very great improvement; for, 
besides. the addition of strength received by 
the gum, the operation was much shortened. 
“ Woven substances that are to be covered 
with the gum, as also the moulds on which 
they are to be placed, ought to be considera- 
bly larger than the bodies they are afterwards 
intended to fit; for, being much contracted 
from absorption of the milk, little alteration 
takes place in this diminution of size, even 
when dry, as about one-third only of the fluid 
evaporates before the gum acquires its solid 
form.” 
From these experiments. Dr, Anderson an- 
ticipated imn)ense benefit to our fishing 
and commercial interests, from the applica- 
tion of the fluid to nets and cordage; and to 
the arts, from its use as a varnish. Still, 
however, there remained the difficulty of pro- 
curing it in sufficient quantities ; partly arising 
from the distance and wildness of the places 
which produced it, and partly from the diffi- 
culty of preserving it. He, therefore, stre- 
nuously urged its cultivation on the coasts of 
Africa, as the nearest tropical locality. No- 
thing, however, came of his zealous and well- 
men t efforts. 
In Nicholson’s translation of “ Fourcroy’s 
Chem stry,” vol. viii. (1804), we have a long 
article on this substance; its remarkable 
fitness to many purposes in the arts is strong- 
ly staled, and itsuses,as it was then employed^ 
are enumerated ; but no better expedient for 
extending its use is suggested than “ to import 
the juice of the hevea with caustic alkali added 
to it,” which prevents the elastic “ substance 
from precipitating;” while it is distinctly said, 
that “ it remains adhesive and viscid in the 
solutions” in fixed oils—that •* when dissolved 
by the oils of lavender, a«pic, turpentine, &c., 
with the assistance of a gentle heat, the viscid 
combination remains adhesive, incapable of 
drying, stiv.king to the hands, and. in fact, of 
no utility” — and that mo.st of the varnishes into 
the composition of which it is made to enter 
by a mixture of fixed and volatile oils, “ have 
the inconvenience of softening and becoming 
very adhesive when exposed to the rays of the 
sun or to heat.” 
That no further advances had been made 
up to 1807, is rendeied highly probable by 
the circumstance that no mention of the sub- 
ject is to be found in the immense collection 
of scientific notices forming the 2d volume 
of Dr. Young’s “ Lectures on Natural 
Philosophy,” more than is implied in giving 
the titles of some of the books we have already 
quoted. Even the substance itself is rarely 
mentioned, and then with very different 
views; while the only notice of water-proof 
cloth is a repetition of Vauquelin’s conjecture, 
that ” the operation w'as performed by means 
of soap, glue, alum, and a lit lie sulphuric acid.” 
No further improvements seem to have 
been attempted before 1820. the date of the 
first patent taken out by Mr. Thomas Hancock. 
It will be observed, that, up to this time, no 
real progress had been made towards tender- 
ing caoutchouc available for popular use, 
owing, on the one hand, to the impossiblity 
of obtaining the liquid juice in a proper state, 
and in sufficient quantities ; and, on the other, 
to the unmanageableness of caoutchouc when 
it had once become solid. 
(To be Continued,) 
