10

INUTILITY OF THUNDER RODS.

Franklin, only recommended addi- ductor. Yet the action of the thuntional pointed conductors to be placed der-rod is confined entirely to the air at nearer intervals. This report, in which immediately surrounds it, and the height of the revolutionary war, the quantity of aerial current which could not be otherwise than displeas- it can produce must evidently be ining to the courtiers, who, from their ferior to what is directed to the point, violent antipathy to the American phi- when held several feet from the conlosopher, were as eager to depre- ductor of an electrical machine But ciate his science as to deride his pa- to avert the stroke, it would be necestriotism. They accordingly set on sary that the whole air between the foot a subscription to enable Mr. Wil- surface and the cloud should be son (father of Sir Robert Wilson) to brought successively in contact with perform electrical experiments on a the top of the rod. Nor is this all; large scale in the Pantheon, and the for the air will be constantly replaced conclusions thence drawn seemed by other electrified portions emitted favourable to the theory of knobs. from the cloud. The effect of the The Royal Society was, in conse- thunder-rod is, therefore, comparaquence, desired by high authority to tively, but a drop in the ocean.* It revise their report; but the Presi- may be easily shown, that, however dent, Sir John Pringle, replied with pointed and tapered, it would require some warmth,that he could not change a thousand years to guard at the disthe laws of nature! Soon after, the tance of a hundred yards; if termiworthy President was given to under- nated with a knob, it might take ten stand, that,since he could not do that, thousand years. Such are the vaunted he had better resign; and he was, performances of thunder-rods, and in fact, so worried on all sides, on ac- such the advantages of their different count of his scientific integrity in this forms! Nor can we appeal to expematter, that he was driven from the rience; it never can be proved that Chair in disgust. thunder-rods have produced benefiSuch sticklers for points and knobs cial effects, but several instances may would have looked amazed to be told, be cited where they have afforded no as we now are, by a person of no less sort of protection. Nay, we shall be authority than Professor Leslie, that convinced, that fully an equal prorods of any kind are nearly altoge- portion of the buildings armed with ther useless. The Professor, in a such supposed safeguards have been paper, which he has written on the struck with lightning. But if thunsubject, in the Edinburgh Philosophi- der-rods are useless, they are also cal Journal, lays it down as a princi- innocent; and that they provoke the ple not to be disputed, that electricity shaft of heaven, is the suggestion of is never communicated in any per- superstition rather than of science. ceptible degree to a remote and un- The cloud exerts an attraction, inconnected body, but by means of a deed, upon the suface of the ground, current of air; and, assuming this but the force depends solely on the to be the fact, he thus proceeds to refute the supposed efficacy of lightning conductors :

distance, and is not, in the least degree, affected by the shape or quality of the substances below. It rolls towards the nearest and most elevated objects, and strikes indiscriminately a rock, a tree, or a spire.

The air, which streams in all directions from the cloud, is dissipated among the more remote portions, and thus gradually communicates its *It appears, from the experiment with electricity. Hence, from the wide the heated ball, (an experiment to prove dispersion, owing to the distance, the that, by means of heat, a ball may be made electricity of the air at the surface of an equally good conductor with a point,) the earth must be weak; and, even that a good kitchen fire has more efficacy in in the midst of the storm, the electrometer is less affected than if placed only a yard behind the prime con

Hence

preventing a house from being struck, than a
whole magazine of thunder-rods.
one of the reasons why a thunder-cloud di-
minishes so fast in passing over a large city.

12 DISCOLORATION OF CORAL ORNAMENTS-SELF-MOVING CARRIAGE.

DISCOLORATION OF CORAL ORNAMEETS. from the velocity of the fly-wheel, It has long been known, that neck- together with the aid of a lever, laces, bracelets. and earrings of which is in the hand of a person in Coral, undergo, after being worn, a front steering, he has not often to very remarkable change, and become put his feet to the treddles." Mr. extremely white and porous. Jewel- M'Donald intends, when he shall lers have no other remedy for this have improved the friction of the deterioration, than to remove the up- body of the carriage, to present the per stratum of coral, till they come same so the Society of Arts; and, as to a depth where no alteration has he desires to receive no emolument been produced. for the same, he hopes it will come into general use.

PLAN OF A STOVE FOR PAPER AND
WOOLLEN-CLOTH MANUFAC-

TURERS, &c.

This change had been ascribed to the action of air and of light; but this was found by experiment not to have been the case: and a discolo. ration never took place, unless when the coral had actually been worn as an ornament; in which case it has It is proposed that the stove shall sometimes been completely whitened, be of cast metal, with a chimney of when used only two or three times the same material continued up to upon the naked skin, and in heated the level of the top of the dryingapartments. A M. Virey, who writes in the "Journal de Pharmacie," ascribes the discoloration and porosity of the coral to the action of a particular acid which exists in the moisture of the body. According to the analysis of Thenard, the acetic; according to Berzelius, the lactic; and according to Berthollet, the phosphoricacid is found in it, under particular circumstances.

room, and that the stove shall have a fire-door and close-door for the ashpit, and an aperture into the ash pit, from a descending flue, brought from the top of the drying-room, and provided with a slide or regulator in it. Let such a stove be placed within an air-chamber, built at the outside of the drying-room, the base of which must he on or below the level of the floor of the drying-room, and extended to its height, four feet in diameter, inside measure, and to be there contracted to a suitable size for a chimney, and then continued to any desirable height. A space must be left open at the base of the airchamber, of the size of the fire and ash-pit doors, to supply the stove with fuel from the outside.

On the side of the air-chamber let there be a descending flue of brickwork, connected at the top and brought down to the floor of the drying-room, and there communicating with a horizontal brick flue, which should run along the centre of the room with branch flues on both sides, provided with regulators in all directions, for admitting warm air into all parts of the room.

The air-chamber has an opening, 18 inches square at the bottom, below the level of the stove, for admitting the air from the outside, which, by coming in contact with the stove and its chimney, will become rarefied, and heated.

CALCULATING THE PRICE OF TIMBER,

1,3

FOR MUSLIN, IJNEN, COTTON, AND,
PROBABLY, SILK OR WOOLLEN, FROM
HORSE CHESNUTS.

The stove is supplied with air, for A PERMANENT BUFF OR NANKEEN DYE, the consumption of the fire, through its descending flue from the top of the drying-room, when its regulator is open; for, by the stove-chimney For the buff colour, take the whole extending, say 10 or 15 feet above the height of the descending flue, the fruit, husk and all, when quite young fire will have the effect of causing (perhaps about as large as a small the steam and rarefied air to descend cherry ;) cut it small, and put it into down that flue, acting on the principle cold soft water, with as much soap as of a syphon, when all other commu- will just cloud or discolour the water. cation to the stove is cut off, which When deep enough, pour off the clear air must be replaced by a supply of part, and dip whatever is to be dyed, air into the drying-room, and (the till it is the colour required. For the Nankeen colour, take the door and windows being perfectly close) can only be had through the husks of the fruit only; cut or break regulators in the warm-air flues them small; steep them in soft water, from the air-chamber; thus producing with soap as above, and dye in the The husks may be a constant and regular supply of same manner. used for the buff dye, after the kerwarm air throughout the dryingWhen the slide or regulator nels are formed; but it is only when in the descending flue, connected they are almost imperceptible that with the stove, is closed, the fire will the whole fruit is used, and the brightgo out, so that no more fuel will be ness of the buff colour diminishes as consumed than circumstances require. the husk ripens, till, when quite ripe, Yours, respectfully, the dye is most like nankeen. Newcastle-on-Tyne.

rooms.

W. H.

It is thought that this, which was discovered by accident many years ago, is not generally known; and that being a permanent, cheap, and easily procured dye, it may be useful, and

SHORT BULES FOR CALCULATING THE supersede, in some measure, foreign

PRICE OF TIMBER.

dyeing stuff. The soap used was white or brown Windsor, and common mottled, whichever was at hand.

Hot water seemed not to answer so well as cold in making the dye, as it was less bright; but once dyed, nothing ever was found to efface the colour. A dyer would easily find the proportions, and, perhaps, some alkali, instead of that of the soap. But if tried at all, it is particularly requested that the directions here given may be strictly followed at first, as they are exactly given by the person who is thought to have made the discovery. Muslin, linen, cambric muslin, and calico, were tried; it did not discharge the colours of printed cottons.

The husks may still be gathered during this month and most of October. Whether any use can be made of them when dry, or whether the dye can be made and kept till the young chesnuts are ready, has not been ascertained.

PROGRESS OF ART-GUNTER'S INEL.

SIR-Your Correspondent, "Unit," inquires, where are 32 and 16?" Let him open the sector, and lay it before him, with that line uppermost, marked N, on the right. In the line marked N find the first 8 from the left, the which, to be readily found, is exactly 4 inches and from the left extremity of the sector, or 1 inch and a half from the opening of the sector towards the left extremity. The 8 being found, the next figure towards the right is a 9, and the next a 1; but the 1, in the example before us, must be called 10; the next a 2, which must be called 20; the 3 must be called 30; and the 4 must be called 40; and so on till the 10 at the end must be called 100. But now let him look back to the second 1, which I before said must be called 10; "Unit" will find the space between the second 1 (10) and the second 2 (20) divided into 10 parts. I may here remark, that 6