Imatges de pÓgina
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copper, and sulphur. After being them), renders the heat insuffer. purified it fells in the market here ablc. for about fifteen rupees per inaund;

.6 I have not loaded this account and I am affured, by many of the with any reflections or conjectures natives, that all the borax in india of my own. I have fimply given comes only from the place above you the narrative of those from mentioned.

whom I had my information; and I am afraid you will think this having put into your poffeffion all at best but a very unfatisfactory and the data I have been able to collect unphilosophical account of the mat- upon the subject, you may make ter; but what can be done, where what we of them you pleale. the only mode of information is “ I shall conclude with a few obthrough some of the wild and un- servations regarding the credibility settled mountaineers ? for the place of the relation : and, first, that it, 1s inaccessible even to the inhabi. is really brought from the Tibbet tants of Hindosan, and has never mountains is certain, as I have mybeen visited by any of them, ex•

self often had occasion to see large cept a tew wandering Faquires, who quantities of it brought down, and have been sometimes led that way, have purchased from the Tartar either to do penance, or to visit mountaineers, who brought it to fome of the temples in the moun. market; secondly, I have never twins. The cold in winter is de. heard of its being either produced fcribed to be so intense that every or brought into this country from thing is frozen up, and that life any other quarter ; and, thirdly, if can only be preserved by loads of it was made on the Coromandel blankets and skins. In the summer coast, as some books mention, I again, the reflection from the fides think there can be little doubt, but of the mountains, which are steep that the whole process would have and close to each other (there being been fully enquired into, and given litle or no plain ground betwixt to the public long before this time."

WILLIS's Method of preventing STONE RETORTS from breaking

during CHEMICAL OPERATIONS.

[From the Fifth Volume of the Transactions of the Society for the

Encouragement of Arts.]

"I

Have always found it neceffary which when dry, are then ready

to use a previous coating for for the proper preserving coating. filling up the interslices of the “ The intention of this first coat. earth or 'stone, which is made by ing is, that the substances thus diffolving two ounces of borax in a spread over, readily vitrifying in pint of boiling water, and adding the fire, prevent any of the distillto the solution as much flaked lime ing matters from pervading the reas will make it into a thin paste; tort, but does in no wise prevent it this, with a common painter's brufli, from cracking. may be spread over several retorts, " Whenever I want to use any

of the above coated retorts ; after I powder of laked line on it, and have charged them with the sub- it immediately fiops the fissure and stance, to be diftiiled, I prepare a prevents any of the dillilling matter thin parte, made with common line from pervading ; even that fubtile feed oil and blaked lime well mixed, penetrating fubitance the folid phofand perfectly plaftic, that it may be phorus will not penetrate through easily spread : with this let the re: it. It may be applied without any torts be covered all over except that danger, even when the retort is red part of the neck which is to be in. hut; and wien it is made a little ferted into the receiver, this is rea- stiffer, is more proper for luting dily dene with a painter's brush; vefleis than any other I ever have the coating will be futficiently dry tries; because if properly mixed, in a day or two, and they will then it will never crack; nor will it in. be fit for use.

durate so as to endanger the break. “ With this coating, I have for ing the necks of the vessels when feveral years worked my stone re. taken off. torts, without any danger of their “ As the above method of prebreaking, and have frequently used serving retorts may be of singular the same retort four or five times; service to philosophical chemists, as observing particularly to coat it over well as those who practise the sciwith the last mentioned composition ence for commercial purposes ; it every time it is charged with fresh is my wish it fhould be generally materials : before I made use of this known; as many curious operations expedient, it was an even chance, may be carried on with greater in conducting operations in itone {nfery, and at an eafier expence. I and earthen retorts, whether they have coninunicated it to the duke did not crack every time; by which de Chaulnes, i ho no doube will means great loss has been fulained. make it known to the French che

“ If at any time during the ope- milts; and thall be happy to hear ration, the retorts should crack; of its being of advantage to a fci. spread some of the oil composition ence so much cultivated in the prethick on the part, and sprinkle some sent age.”

Dr. RUSTON's Letter to Dr. FRANKLIN on the CURE of SMOKY

CHIMNEYS.

"

[From Dr. FRANKLIN's Philosophical and Miscellaneous Papers.) HE subject of smoky chim

“ A froky house and a soviding wife, neys,

of which I had the Are (faid to be) two of the greatett honour of conversing with you at

ills in life." your own house last evening, is of 66 And however difficult it may fo much imporiance to every indi. be to remedy one of thofe ills, yet vidual, as well as to every private any advances we may be able to family, that too much light cannot make towards removing the inconbe thrown upon ito

veniences arising from the other, cannot fail to be favourably received I then thought of contracting thera by the public. As they are shortly below, but as the method of con. to be favoured with your sentiments tracting them in front to the size of on that subject, potlibly the follow- a final coal-fire grate has an uning observations, which were in fightly appearance, as it makes a fact occafioned by necetlity, and are disagreeable blowing like a furnaco, the result of my own experience, and as it is the occasion of consum. may not be altogether undeserving ing a great deal of unnecessary fuel, of notice.

the heat of which is immediately “When I left London and went hurried up the chimney, I rejected to live in Devonshire, in the latter this method,' and determined to end of the year 1777, it happened contract them above, a little out of to be iny lot to dwell in an old light. For this purpose I threw an mansion which had been recently arch across, and also drew them in modernised, and had undergone a at the sides. This had some effect, thorough repair. But as in most but as this contraction was made of the old houses in England, the rather suddenly, and the finoke, chimneys, which were perhaps ori- by striking againit the corners that ginally built for the purpose of were thereby occasioned, was aptito burning wood, though they had recoil, by which means fome part been contracted in front, fince coal of it was thrown out into the room ; fires came into general use, to the I determined to make the contracmodern size, yet they were still, tion more gradually, and therefore above, out of light, extravagantly run it up at the back, where the large. This method of building depth of the chimney would admit chimneys may perhaps have an- of it, and also fhelving or floping swered well enough while it was in a conical kind of dire&tion at the the custom to fit with the doors fides, as high as a man, Itanding and windows open; but when the upright, could conveniently reach, customs and manners of the people and by this means brought the cabegan to be more polished and re- vity within the fpace of about twelve fined, when buildings and architec- by fourteen or fixteen inches, which ture were improved, and they began I found fufficiently large to admit a to conceive the idea of making their boy to go up and down to sweep chambers close, warm, and com- the chimneys. This method I fortable, these chimneys were found found to succeed perfectly well, az to smoke abominably, for want of to curing the chimneys of finoking, a sufficient supply of air. This and it had this good effect, of mak: was exactly the case with the house ing the rooms considerably warmer; in which I first lived, near Exeter, as this experiment succeeded so and I was under the necessity of well, since the only use of a chiin, trying every expedient I could think ney is to convey away the finoke, of to make it habitable.

I determined to carry it still farther, 66 The first thing I tried, was in order to ascertain, with precision, that method of contracting the chim- how much space is absolutely neneys by means of earthen pots, cessary for that purpose, because all much in use in England, which are the rest that is shut up must be so made on purpose, and which are much gained in warmth. Accord. put upon the tops of them; huc ingly I laid a piece of Nate acr ifs his method by no means aafwerød. the remaining aperture, removable

13

at pleasure, so as to contract the attending the contraction of the space above two thirds, leaving chimney in the front parlour, which about three inches by twelve remain- deserves to be attended to; which ing open ; but this space, except was, that before I applied the cait when the fire burnt remarkably iron plate, which I made use of in. clear, was scarcely susñcient to carry stead of late, to diminish the face away the smoke. I therefore en- requisite for a chimney-sweeper's Jarged it to half the space, that is, boy to go up and down, the suction to about fix by feven or eight inches, or draught of air was so great, that which I found fully futhicient to it was with difficulty I could flut carry away the smoke from the the door of the room, infomuch largest fires.

that I at first thought it was owing 6 When I removed into the Bed

to a tightress of the hinges, which I ford Circus in Exeter, though the imagined must be remedied; but uphouse was modern, and almoit per- on applying the iron plate, by which fectly new, yet the chimneys were the space was diminimed one half, large ; in consequence of which the door Mut to with the greatest almost every room of it smoked. ease. This extraordinary pretiure My predecessor, who was the first of the air upon the door of the inhabitant, had been at great ex- room, or suction of the chimney, I pence in patent itoves, &c. but take to be owing in some measure without effect; but by adopting the to the unusual height of the house. method I have just now described, Upon the whole, therefore, I not only cured every chimney of this fact seems clearly ascertained, smoking, but my house was remark- viz. That the Hue or fize of the ed for being one of the warmet chimney ought always to be proand most comfortable to live in of portioned to the tightness and close. any in that large and opulent city. nefs of the room : fome air is un

i. The house I now live in in Phi- doubtedly neceffary to be admitted ladelphia, I am tuld, has always into the room in order to carry up had the character of being both the smoke, otherwise, as you juftly cold and smoky; and I was con- observed, we might as well expect vinced, as soon as I saw the rooms smoke to arise out of an exhauited and examined the chimneys, that receiver ; but if the flue is very it deferved that character ; for large, cither the room is tight, and though the rooms were close, the the finoke will not afcend, or it is chimneys were large : and ue Mall pretty open, and the consequence ever find, that if our chimneys are will be, that the air of your room large, our rooms will be cold, even will be fo frequently and to con. though they should be tolerably ftantly changed, that as fast as it is close and tight; because the constant heated, it will be hurried away, with rushing in of the cold air at the the smoke, up the chimney, and of cracks and crevices, and also at course your room will be constantly every opening of the door, will be cold. sufficient to chill the air, as fast as “One great advantage attending it is heated, or to force the heated this method of curing smoky chimair up the chimney; but by con- neys is, that, in the first place, it tracting the chimneys I have cured makes no awkward or unfightly apit of both these defe&ts There pearance, no:hing being to be seen was one remarkable circumstance but what is usual to chimneys in

com.

common ; and, in the second place, principles upon which chimneys that it is attended with very little ihould be erected ought to be thoexpence, a few bricks and mortar, roughly understood, it is to be with a plate or covering to the hoped, that not only this expence, aperture, and a little labour, being fmall as it, but that all the other all that is requilite. But in this inconveniences we have been speak, new country, where crops of houses ing of, will be avoided, by conmay be expected to rite almo!t as fructing the flues of the chimneys quick as ficids of corn, when the sufficiently finall."

THOUGHTS on the CAUSE of the VARIATION of the NEEDLE.

[From CAVALLO's Treatise on Magnetisım.]

HIS wonderful phenomenon cooling of the magnetic bodies in "of ; vered, employed the thoughts of which was in confequence of his very able philosophers ; many hy- having first observed, that the acporhefes having been offered, not rion of the magnet on the needle only for its explanation, but even was diminished by heating, and into foretel the future variations in creased by cooling. various parts of the world. I need “ Following Mr. Canton's judi. not detain my reader with a parti- cious method of deriving the excular hittory of thole hypothefcs; planation of natural appearances but fall only observe, in general, from properties actually proved by that neither have their predictions experiinents, I think, that the inansivered, nor were any of them create and diminution of magnetic founded upon evident principles. attraction, by heating and cooling The fuppofition of a large magnet of the magnet, as obierved by Mr. being inclosed within the body of Canton, together with the relult of the earth, and of its relatively mov- the experiments described in the ing with respect to the outward thiell preceding chapter, seem fully fuffior cruit; the fuppofition of there ent to account for the general variabeing four moveable magnetic poles tion of the needle. within the earth; the hypothetis of “ If we collect under one point a magnetic power, partly within of view all the causes hitherto afand partly without ihe surf.ce of certained, which can increase or the earth; together with several diminish the attraction between or her hypotheses on the fame fub- magnetic bodies, we shall find, that ject, are not only unwarranted by the attration between the magnet actual experiments, but do neither and iron, or between magnet and seem analogous to the other opera magnet, is increased by cooling, by tions of nature. The late ingeni- a regeneration of iron, or phlogisous Mr. Canton, F.R.S. was the tication of its cals, and, within first, who endeavoured to account certain limitations, by the action for the daily variation of the mag. of upon the iron; that this netic needle by the heating and attraction is diminished by heating,

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