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_Heating with Hot Water._
Mr. A.M. Perkins has communicated to the _Gardeners' Magazine_ the
details of his plan for heating hot-houses by the circulation of hot
water in hermetically sealed tubes of small diameter. Upon the economy
of the plan, Mr. Loudon observes:--"With respect to the power of the
one-inch tubes, it has been demonstrated by a mathematician and chemist
of the very first authority, that as much will be effected by one of Mr.
Perkins's one-inch tubes, heated to 300° as by one of the three-inch
tubes, employed in any of the ordinary modes of heating by hot water
when heated to 180°." A second advantage of Mr. Perkins's mode for
hot-houses, is the small space which the pipes occupy. A third advantage
is, that the water may be circulated without regard to whether the tubes
are below or above the level of the fire-place. "But, however favourable
this plan may be for heating hot-houses, the advantage for that class of
structures are as nothing compared to those which it offers for heating
_dwelling-houses_ and all kinds of _manufactories_. This will be
understood at once, when it is stated that the water may be circulated
under ordinary circumstances of attention to the fire, at from 300° to
600°; and, with extraordinary strength of pipe, and application of fuel
to a still higher degree. It is found that 400° will roast meat. The
workmen in the bank-note printing-office of Messrs. Perkins and Bacon
have dressed a beefsteak at the further extremity of the pipe of hot
water used for heating the steel plates; and Mr. Perkins is constructing
for himself an oven for roasting by water. It is easy to see, that, in a
very short time, this will lead to extraordinary and most beneficial
changes in domestic arrangements; and that if we could get rid of our
prejudices in favour of open fires, the smoky atmospheres of our great
towns would be got rid of at the same time. Water at 500°, or, at least,
water at 300°, for the purposes of cookery, and for heating reserve
cisterns of cold water, or masses of metal or masonry, for various
domestic purposes, including warming rooms, heating baths, laundries,
&c. may, at no distant time, be circulated by companies, in the same
manner as gas; and, in London, instead of one fire for every room, as at
present, there may be only one in a parish, or in every square of an
acre in area."
_A Marine Railway_
for the purpose of conveying vessels overland, has been projected by Mr.
Henry Fairbairn, in the United Service Journal for May, 1832. The
vessels are to be raised from the sea by machinery, placed in slips and
dragged along the railway by locomotive steam-engines. The same author
proposes to connect Ireland with Scotland, by means of a bank between
Portpatrick and Donaghadee; and England with France, by means of a chain
bridge, causeway, or tunnel, from Dover to Calais. Over all the lines of
marine railways he proposes to form suspension railways, resting upon
arches, in the manner of Mr. Dick's, for the conveyance of passengers,
mails, and merchandise.
_Silk from Spiders._
At the last Anniversary of the Society of Arts, the Silver Isis Medal
was presented to Mr. D.B. Rolt for obtaining Silk from the Garden
Spider. We find the details in the volume of the Society's
_Transactions_ lately published.
"The subject of Mr. Rolt's experiments has been the garden spider,
Aranea diadema, the webs of which, in autumn, are so conspicuous on the
surface of shrubs and in other similar situations. On allowing one of
these animals to crawl over his hand, he found that it drew a thread
with it wherever it went: he likewise, without any difficulty, wound
some of this thread over his hand, finding that the spider continued
spinning while the thread was winding up.
"On this hint, he connected a small reel with the steam-engine of the
factory in which he is occupied, and putting it in motion, at the rate
of 150 feet per minute, found that the spider would thus continue to
afford an unbroken thread during from three to five minutes. The
specimen of this silk, which accompanies Mr. Rolt's communication, was
wound off from twenty-four spiders in about two hours. Mr. R. estimates
its length at 18,000 feet; its colour is white, and its lustre is
brilliant, and completely metallic, owing, probably, to its great
opacity. No attempt has been made by him to combine two or more
filaments into one by winding, nor, of course, to form it into thread by
throwing.
"The thread of the garden spider is so much finer than that of the
silk-worm, that the united strength of five of the former is, according
to Mr. Rolt, equal only to one of the latter; and, assuming that the
weight is in proportion to the strength, and that a spider will yield
twice a-year a thread 750 feet long, while that produced by a single
silk-worm is 1,900 feet, it follows that the produce of one silk-worm is
equal to that of 6.3 spiders. Now, as on an average it takes about 3,500
silk-worms to produce a pound of silk, it would take about 22,000
spiders to produce an equal quantity. Besides, spiders are not so easily
confined as silk-worms, and whenever two come in contact, a battle
ensues, which ends in the destruction of the weaker one. Spiders kept
for silk must, therefore, be each in separate dens or cells; and the
apparatus contrived by Mr. Rolt for this purpose, although very
ingenious and well adapted to carry on a course of experiments with a
hundred or two, would manifestly be wholly inapplicable to any purpose
of commercial utility. Mr Rolt has, however, made some interesting
additions to the history of the garden spider, and has obtained the silk
in its natural state, exhibiting all its peculiar lustre; his method,
likewise, of winding the silk directly from the animal is, to say the
least of it, effectual and ingenious."
It should be added that "the Society are of opinion that it will never
be possible to employ spiders' silk, beautiful as it is, in any
profitable manufacture; but have thought proper to confer a reward on
this gentleman for his communication, as forming an interesting addition
to the natural history of the spider."
_Medicinal Employment of Holly Leaves._
Dr. Rousseau has obtained from the Medico-Botanical Society of London
its silver Medal, for an essay on the effects of holly leaves in fever:
he has cured several intermittent fevers by the remedy, whose alkali he
calls Ilicine.--_Gazette of Health._
_Tobacco no security against Cholera._
M. Chevalier proved, from documents, that the assertion made on a former
evening, that tobacco was a preservative against cholera, was erroneous.
He stated that twenty-seven mechanics employed in the tobacco
manufactories had died of the disease.--Ibid.
_Prussic Acid a Poison to Vegetables._
The sensitive plant, when exposed to the vapour of prussic acid,
instantly closes its leaves. The same plant, as well as other tender
plants, such as the garden pea and kidney bean, when subject to the
influence of this acid, quickly wither and die, and the laurel-water has
the same effect upon them. It appears also that plants which naturally
contain the acid, such as the cherry-laurel and almond tree, are not
less susceptible of its poisonous action than others. Seeds, steeped for
some time in the acid, lose their power of germination.--Ibid.
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