having known it recently tried by others, but without being informed of their fuccefs. I have reafon to think this valuable drug will, by this method, be brought much fooner to perfection than from feed.

Method of curing Rhubarb.

The plants may be taken up either early in the fpring, or in autumn, when the leaves are decayed, in dry weather if poffible, when the roots are to be cleared from dirt (without washing): let them be cut into pieces, and with a fharp knife freed from the outer coat, and expofed to the fun and air for a few days, to render the outfide a little dry.

In order to accelerate the curing of the largest pieces, a hole may be fcooped out with a penknife: thefe and the fmaller parts are then to be ftrung on packthread, and hung up in a warm room (I have always had the conveniency of fuch a one over a baker's oven) where it is to remain till perfectly dry. Each piece may be rendered more fightly by a common file, fixing it in fmall

vice during that operation: afterwards rub over it a very fine powder, which the fmall roots furnish in beautiful perfection, for this and every other purpose where rhubarb is required.

which the fociety had offered on the production of yeaft, of which you obligingly gave him full information. As I found November was the month in which the matter was to be decided, I deferred troubling you any more till I had caufed an experiment to be repeatedly tried; which a domeftic of mine, who brews for me, had at that time first made.

I had just before, with his affiftance, impregnated wort with fixed air, or rather a decoction of malt in water, according to Dr. Henry's ingenious method, and by the yeaft thereby obtained, produced good bread. This led him, unknown to me, to try whether the experiment would not fucceed full as well without fixed air; which he found it did. He accordingly brought me a fmall veffel with a full head of yeaft upon it, affuring me with fome degree of exultation, that neither oil of vitriol with chalk, nor any portion of old yeast, had been employed on the occafion. This greatly furprised me; and I then defired he would proceed with the experiment in his own way, and endeavour to increase the quantity already made, by what additional decoction of malt and water he might think proper; infifting only that nothing but malt, water, and heat, fhould be employed for the purpose. He did fo, and in a few days increased the original quantity

till it became fufficient to work a

hogfhead of fmall-beer, which pro duced ten pounds weight of perfect yeast; and this, being foon after put on a vat for a hogfhead of ale, was found to be augmented to forty-two pounds.

The

zdly. That it be kept in an equal degree of heat. And,

3dly. That, when the fermentation is begun, it fhould be affifted and augmented with fresh decoctions of the fame liquor."

The proportions and method which my fervant has found generally to fucceed, I will now give you, as taken from his own words, in the form of a recipe.

Procure three earthen or wooden veffels of different fizes and apertures, one capable of holding two quarts, the other three or four, and the third five or fix: boil a quarter of a peck of malt for about eight or ten minutes, in three pints of water; and when a quart is poured off from the grains, let it ftand in a cool place, till not quite cold, but retaining that degree of heat which the brewers ufually find to be proper when they begin to work their liquor. Then remove the veffel into fome warm fituation near a fire, where the thermometer ftands between 70 and 80 degrees (Fahrenheit) and there let it remain till the fermentation begins, which will be plainly perceived within thirty hours; and then two quarts more of a like decoction of malt, when cool, as the first was; and mix the whole in the larger-fized veffel, and ftir it well in,

which must be repeated in the ufual way, as it rifes in a common vat: then add a ftill greater quantity of the fame decoction, to be worked in the largest veffel, which will produce yeaft enough for a brewing of forty gallons.

P. S. It may be proper to add, that my fervant is of opinion, that a proper quantity of hops boiled in the liquor, makes the fermentation proceed better; but as it may, and has actually fucceeded without fuch addition, I would willingly with them to be omitted, to prevent the bread baked with it from tafting bitter. Experience only can decide this; and farther experience is ftill wanted, to make a perfect recipe for the operation.

Dear Sir,

ACCORDING to my promife, I write to inform you of the refult of fome more experiments which have been made here, under my direction, relative to yeaft; and the rather, because they were made by means of a very fimple apparatus, which I think will be found very conve nient on fhip-board, and alfo in cottages, &c. It is merely a wooden box, of about twelve or fourteen inches fquare, open on one fide, in which a veffel containing the wort is placed; and then the box is fet with the open fide close to a wall, heated by a fire on the other fide, when the thermometer indicates the wall to be about 80°: fo that I imagine the back of a chimney in a fhip, or behind an oven or kitchenfire in a cottage, would be found very convenient for the procefs; as the veffel might be there furrounded with a small atmosphere of air, sufficiently warm at the firft, and capable of being continued at the

fame

fame equable temperature for a fufficient time.

A box of this kind, in which the following experiments were made, was placed on a dreffer in my kitchen, more than eighteen feet from the kitchen-fire, but against a thin wall, which divides the kitchen from the fervants hall, juft behind the fire-place of that room; and the open fide of the box turned to the heated wall, the veffels themfelves uncovered. If you recollect the trouble you fo obligingly took in heating your office, you will think this method, fince difcovered, of performing the fame experiment, of confiderable utility.

Experiment ift.-Three veffels were fet at the fame time in the warm box, containing a quart of liquor each, and of equal ftrength with respect to malt: one was a decoction without hops, another with hops, the other a fimple infufion of malt: in about twenty-four hours the hopped decoction produced a fine head of yeaft; the other decoction fermented as well, but was twenty-four hours later; the fimple infufion was near thirty-fix hours later, and the yeast appeared dark and ill-coloured, fo that my houfekeeper thought it fpoiled; but this bad appearance was merely owing to its not having been boiled and cleared, for it made very light breakfast rolls.

This experiment, you will perceive, was made to try whether hops (as my fervant imagined) were neceflary; and it certainly proves that they accelerate the fermentation; but it proves also, that neither hops nor boiling are effential to the procefs.

1

Experiment 2d. - Four veffels from a common brewing of ale

were placed in a box of longer dimenfions; one contained two quarts; a fecond, one; a third, a pint; a fourth, half a pint: they all fhewed figns of fermentation at the fame time, viz. in about twenty-four hours; but that in the mug or pot holding a pint appeared the strongeft, which my fervant thought was owing to the fmaller diameter of the veffel, which was fmaller in proportion to the half-pint; but as it ftood more centrally to the heat of the fire behind, I am perfuaded the excefs of fermentation proceeded from that caufe. This proves that the quantity you begin the process with is not very material: though two quarts feem to be moft convenient for the purpose of baking.

Experiment 3d, Was inftituted merely to find whether an addition of fugar would accelerate the fermentation; for which purpose, two quarts of Lopped liquor were tried in feparate veffels, a quart in each: and the refult was, that the decoction, in which two large spoonfuls of coarse fugar were stirred in, did not ferment in the leaft, though continued in the warm box five days and nights; the other fermented in about thirty-fix hours. The reason of this later fermentation than of that in the former experiments, was, that the liquor ufed was from a brewing of fmall-beer. Hence we may conclude, that a decoction of the ftrength of ale, if not of strong beer, is the best to begin with.

Account of Experiments on the Generation of Yeaft, made under the InSpection of the Committee of Chemiftry, in the Month of November 1789.

FOUR quarts of ground malt were put into a new ftone ware veffel, and mafhed with about an equal quantity of hot water in the ufual manner for brewing. When

the mash had stood about an hour, the wort was drawn off, and three quarts of boiling water poured on the grains; when this had stood a due time, the liquor was fuffered to run off, and the whole liquor boiled half an hour; being then fet to cool, was poured clear from the fediment, and then put in a room where the heat was regularly kept up to fummer heat, or near 8c of Fahrenheit's thermometer. It flood in this degree of heat till fome figns of fermentation appeared on the furface; which came on in about three days.

Another brewing was then made as above described; and, when of a due heat, ftirred into the former liquor. In about twenty-four hours fome yeaft appeared, and another brewing was then made; and, when of a due heat, mixed with the two former ones, and well beat in, the heat being fill kept up to the degree above mentioned: in about two days more, five ounces of excellent yeast were collected from the furface of the liquor.

Some of this yeast being mixed with a due proportion of flour, water, and falt, anfwered all the purpofes intended for bread; and might certainly have been equally well applied to brewing, in the common method. In fine, being pure and good yeaft, it will anfwer all the intentions of that useful article.

Report of the Committee on Dr. Hunter and Mr. Hornby's Process for producing an ardent Spirit from Gar

WE have examined the fample of fpirits, which was fent by Dr. Hunter of York to the Royal Society, and we have read the account of the experiment on the fermentation and distillation of carrots, by which the faid fpirit was produced. The experiment was made by Mr. Thomas Hornby, druggift in York, with one ton and eight ftone of carrots, which, after being expofed to the air a few days to dry, weighed 160 stone, and meafured 42 bufhels; they were washed, topped and tailed, by which they loft in weight 11 stone, and in measure seven bufhels; being ther cut, they were boiled with the proportion of 24 gallons of water to one third of the above quantity of carrots, until the whole was reduced to a tender pulp, which was done in three hours boiling. From this pulp, the juice was eafily extracted by means of a prefs, and 200 gallons of juice were produced from the whole. This juice was boiled again, with one pound of hops five hours, and then cooled to 66 of Fahrenheit, and fix quarts of yeast being added, it was fet to ferment. The ftrong fermentation lafted 48 hours, during which time the heat abated to 58 of Fahrenheit; 12 gallons of unfermented juice, which had been referved, were then heated and added to the liquor, the heat of which was thus raised again to 66, and the fermentation was renewed for 24 hours more, the air of the brewhoufe being all this time at 46 and 44. The liquor was now turned, and continued to work three days from the bung; and, laftly, it

was

was diftilled, and the firft diftillation was rectified next day without any addition. The produce was twelve gallons, of the fame quality with the fample.

In our examination of this fample, we found it resembled a corn fpirit in flavour, but was equal to a corn fpirit of the best kind, and it was a proof fpirit.

The refufe of the carrots weighed 48 ftone, which, added to the tops and tails, made provifion for hogs, befide the wafh from the ftill, which measured 114 gallons.

From this experiment, Dr. Hunter draws the following comparison be

tween the diftillation of carrots and that of grain.

Twenty tons of carrots, which

will make 200 gallons of proof fpirits, may be bought for 161.

Eight quarters of malt, or rather the materials for diftiliation, confifting of malt, wheat and rye, may be bought for 161. and will alfo make 200 gallons of proof fpirit.

The refufe from the carrots will

be 960 ftone, which, at 1d. per ftone, will fell for 41.

The refufe or grains from the malt, &c. will be 64 bufhels, each bufhel weighing about three ftone," which, at Id. per ftone, will fell

for 16s.

SIR,

TH

Tytherton, Dec. 3, 1789.

HE following is as near a calculation of the expences of rearing my calves without milk, as I can at present affert. In the calves, in 1788 twenty-three, and year 1787, I weaned feventeen in 1789, fifteen ditto. I bought in 1787, three facks of linfeed; I put one quart of the feed to fix quarts of water, which, by boiling ten minutes, became a good jelly; this jelly is mixed with a fmall quantity of the tea of the beft hay fteeped in

boiling water.

Having my calves drop at different times, I did not make an exact calculation of the expence of this hay tea, but out of my three facks of feed, I had better than two bufhels left at laft. I gave them the jelly and hay tea three times a them 6 d. per day; the price of the day; to the boy who looked after linfeed was 4s. 6 d. per bushel; the whole three years feed 21. 5 s.

My calves are kept in a good growing ftate, and are much better at this time than my neighbours' that are reared by milk; they do not fall off fo much when they come to grafs.

I am your obedient fervant,
THOMAS CROOK.

General Rules for the Choice of Spectacles, and for the Prefervation of the Sight. From Adam's Effay on Vifion.

HE most general, and perhaps the best rule that can be

TH