128

MISCELLANEOUS NOTICES.

Eye of the Whale.-The substance constituting the surface of, and surrounding the cavity which incloses the crystalline humour in the eye of this animal, is so compact and strong, that it is difficult to cut it with the sharpest kuite. But for this solidity it would be unable to sustain the enormous pressure to which it is subjected at great depths in the ocean. Supposing the part of the eye-ball exposed to the water to contain six square inches superficial, the pressure upon it, at a depth of 8400 feet (to which depth whales have been known to dive), is equal to twenty-three thousand one hundred pounds weight.

Large Diamonds.-The number of known diamonds, weighing 36 carats and upwards, is said to be no more than 19. The two largest of these are in the possession of the Royal Family of Portugal. One is still uncut, and, if we may credit the Portuguese accounts, is the largest ever found. It is said to weigh 1680 carats, and, supposing it to lose half its weight in cutting, would be worth 5,644,8007. There is a small part broken off, which was done accidentally by the man who found it, in the Brazils. The other diamond, in the possession of the House of Braganza, is estimated to be worth 3,698,0007.

Charcoal a Substitute for Peruvian Bark.The New England Journal of Medicine points out a number of striking analogies between the Peruvian bark and charcoal, in their effects on the human system. Both of them serve equally to stimulate the appetite, prevent the recurrence of febrile paroxysms, and correct morbid associations; and both cease to have any beneficial effect after long continued use.

White Wax and the Lily.-The Kings of France anciently reserved to themselves the right of sealing with white wax, and it was only on extraordinary occasions that they granted the privilege to others, which was done by Letters Patent.

Fire Proof Envelope.-We mentioned (we believe), sometime ago, that Professor Aldini was stated to have discovered a means by which firemen might set at defiance the flames of a house on fire. It is now said to consist in their making use of a full suit of mail, composed of a mixture of metal and asbestos; and we are assured that in some experiments which were made at Milan, men thus protected, remained without any inconvenience, five minutes, in the midst of a fire sufficiently powerful to consume an unprotected body in that time, and even walked without injury over an iron grating placed over blazing faggots. About ten years ago, some philosophers in the Netherlands, taking a hint from our coal miners' Davy, proposed that firemen should make use of iron-wire clothing, with meshes of extremely small dimensions; and we remember to have read the details of a number of experiments, which proved that persons thus enveloped could sustain a very extraordinary degree of heat, without being either roasted or catching fire. We suspect that Professor Aldini's invention is only a revival of this old plan, in (perhaps) an improved shape. Something useful in this way may be reasonably hoped for between them.

Poisonous Cider-The eldest son of a respectable farmer near Honiton lately fell a victim to the drinking of cider, which had been made from a press with a leaden bed or dish; the necessary effect of which is, that the malic acid contained in the cider exerts a powerful chemical action upon the metal-forming the malate of lead, a destructive poison. Persons should not buy any cider until they have seen the press from which it has been made, and ascertained that the bed is of wood.-North Wales Chronicle.

Dear-bought Treasures.-In the memoirs of General Miller's service in Peru, there is a calculation, that the lives of no less than eight millions two hundred and eighty-five thousand Indians were sacrificed in that province alone, in searching for gold and silver to enrich their tyrannic masters, the Spaniards. The persons thus employed, used to be drawn by ballot, and so severe was their labour, that they were generally killed off in the course of twelve months.

MINOR CORRESPONDENCE.

Clock without Wheels.-Sir,-Your correspondent, "R. S." in Number 265, 6th Sept. has given a description of a clock without wheels. The primary principle he states to be a piece of caoutchouc, or Indian rubber. I shall feel obliged to him if he will explain in what manner the rubber acts to produce the motion of the index; and how the weights are acted upon by the rubber; also, the size of the piece of rubber, and The the exact weight of the pieces of lead. manner of applying the bell is likewise very dosirable to know.-I am, &c. A.

Will-o'the-Wisp. -Sir,-1 was much pleased with reading an account of the "Will-o'theWisp," which appeared in a recent Number of the "Mechanics' Magazine," having, myself, seen the same near Barham, in the county of Kent. The statements in your valuable work, I know to be correct; and as many individuals doubt of the existence of an animal, or creature, termed "Will-o'the-Wisp," you will much oblige me by giving publicity to this confirmation of the fact. In consequence of the correctness of the case, I have requested my bookseller to forward me three dozen copies for distribution, to satisfy the inhabitants of the city of Canterbury, that a "Will-o'the-Wisp" has been seen, and minutely examined, in other counties as well as Kent. The representation of it in your work is exactly what I have myself witnessed, though doubted by most persons to whom I have related the circumstance. I remain, &c., HENRY HORN.-Burgate-street, Canterbury, Sept. 13.

Submarine Plants.-Sir,-There is a letter extant in the British Museum, from the celebrated John Locke to Sir Hans Sloane, in which, alluding to some History of Plants that was about to be published, he says, "I hope the author, in his account of Submarine Plants, will not omit to tell us how deep under water any of them are to be found, or whether they, or any species of them, are at any depth we can come at; for I am apt to suppose that thejair hath something to do with vegetation under water." I should be glad to learn whether the doubt here started has yet been resolved by naturalists ?-I am, &c. Bookworm,

INTERIM NOTICES.

An answer to "F." has been left with our Publishers.

S. C. The paper alluded to is under consideration.

W. H. H. will find a note Jaddressed to him at our Publishers, any time after the 25th inst."

Communications received from Mr. BroughMr. Doull-H. M.-Arias-Mr. Frey (of Basil)Mr. Jopling-G. S.-Mr. Barnard-F. M.-G. M. Henry D.-Mr. Badham.

Erratum.-P. 83, col. 2, 1. 38, after the word "straps" insert "come alternately."

Communications (post paid) to be addressed to the Editor, at the Publishers, KNIGHT and LACEY, 55, Paternoster Row, London.

Printed by G. Duckworth, 76, Fleet-street.

Mechanics Magazine,

MUSEUM, REGISTER, JOURNAL, AND GAZETTE.

No. 268.]

SATURDAY, SEPTEMBER 27, 1828.

[Price 3d.

"It is the bounty of Nature that we live, but of philosophy that we live well, which is, in truth, a greater benefit than life itself."-SENECA.,

130

PERKINS'S LATEST STEAM-ENGINE IMPROVEMENTS.

MR. PERKINS'S LATEST STEAM-
ENGINE IMPROVEMENTS.

No. 2.

(From Designs and Communications by Mr. C. DAVY.)

(Concluded from our last.)

He has,

He

We now proceed to elucidate the construction of various parts of this engine in detail, and would first advert to Mr. Perkins's valuable observations as to the causes of the many dreadful explosions of steam boilers, and their fatal consequences-loss of life. It appears, by the numerous experiments of Mr. Perkins, that a fact, hitherto supposed to be well established, has been controverted; namely, "that the caloric, or heat of steam, at a given elasticity, is invariably the same when in contact with water." by experiment, proved that steam may be generated to very high degrees of temperature without a corresponding increase of power. illustrates the theory of sudden explosions, by supposing that, from want of a regular supply of water to the boiler, the water sinks below those parts which ought to be completely covered by it; which parts, being left uncovered, become much hotter than the water itself; and as caloric will not descend in water, "it cannot be taken up" by the water which is below it. The steam becomes accordingly, in this instance, so much surcharged with heat, as to heat the boiler red hot. But should the water, by any means, be made to take up the excess of heat contained in the steam generated, as well as the heat contained in the upper part of the boiler, by drawing off the steam, so as to allow the water to rise, by relieving the pressure; the water would instantly, in coming in contact, flash into steam of such power, that no safety valve whatever could prevent an explosion. It probably may be in the recollection of many, that a shocking steam boat accident happened at the very time the steam was being blown off, after its journey was completed, occurrence which seems to substantiate the statement of Mr.

-an

Perkins, namely, that the pressure of steam being removed instantaneously from the surface of the water, allows the latter to rise and be converted into highly elastic steam, which produces the dreadful consequences before mentioned. Boilers, too, as they are ordinarily constructed, occupy much space, and the room in which they are situated is not unfrequently filled with lumber, one of the most injudicious things possible; for it cannot be too often repeated, that wood, and other combustible substances, have been ignited by being in contact with the boiler under such circumstances.* As an observation was made,† that I had not been sufficiently explicit as to the mode adopted by Mr. Perkins for generating high pressure steam with safety, I shall now proceed to fill up the void.

Fig. 1 is a front elevation of the furnace. Fig. 2 is a longitudinal section of the same.

The generators consist of 3 tiers of bars of cast iron, 8 feet long and 5 inches square, having holes cast through them, 14 inch diameter, lying horizontally in the furnace. They have also communications with each other in the front and rear, where they are so connected as to allow the water to be forced through each of the upper tiers, previously to its being flashed into steam in the lower tier. The connexions are formed as shown in the diagram, fig. 5. The connecting pieces, marked a a, and the long tubes bb, are entirely enclosed in the furnace, and are fastened by the flanges on the outside, c c d, fig. 1; so that, should the pipes become loosened, they may be drawn together by the adjusting screws. By the operation of the force pump (see last Number), the water is injected into the two upper tiers

• A most destructive fire happened some time since, which destroyed extensive premises belonging to a friend of mine; and, although the cause was never ascertained, I always considered it to have originated in the boiler house, which had been injudiciously made a repository for all sorts of lumber. † Vol. vii. p. 387.