other decoction fermented as well, but was twenty-four hours later; the fimple infufion was near thirtyfix hours later, and the yeaft appear ed dark and ill-coloured, fo that my housekeeper thought it fpoiled; but this bad appearance was merely owing to its not having been boiled and cleared, for it made very light breakfaft rolls.

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

Experiment II. 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 thewed 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 ftrongeft, which my fervant thought was owing to the fmaller diameter of the veffel, which was fmallet in proportion to the half-pint; but as it flood 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 procefs with is not very material: though two quarts seem to be moft convenient for the purpose of baking.

Experiment III. was inftituted merely to find whether an addition of fugar would accelerate the fermentation; for which purpofe, two quarts of hopped liquor were tried in feparate veffels, a quart in each: and the refult was, that the decoc

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

When the mash had stood abost an hour, the wort was drawn off, and three quarts of boiling water poured on the grains: when this had ftood a due time, the liquor was fuffered to run off, and the whole liquor boiled half an hour; being then fet to cool, it was poured clear from the fediment, and then put in a room where the heat was regularly kept up to fummer heat, or near 80° of Fahrenheit's thermometer. ftood in this degree of heat till fome figns of fermentation appeared on the furface; which came on in about three days.

It

Another brewing was then made as above defcribed; and, when af 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

Tis a fact which has been long known, that clays, and feveral other incombuftible fubftances, when mixed with fea_coal, in certain proportions, caufe the coal to give out more heat in its combuftion than it can be made to produce when it is burnt pure or unmixed; but the cause of this increase of heat does not appear to have been yet in veftigated with that attention which fo extraordinary and important a circumftance feems to demand.

Daily experience teaches us that all bodies, those which are incombuftible,-as well as thofe which are combuftible, and actually burning,-throw off in all directions heat, or rather calorific (heat-making) rays, which generate heat wherever they are ftopped, or abforbed but common obfervation was hardly fufficient to how any perceptible difference between the quantities of calorific rays thrown off

by different bodies, when heated to the fame temperature, or expofed in the fame fire; although the quantities fo thrown off might be, and probably are, very different.

It has lately been ascertained, that when the fides and back of an open chimney fire place, in which coals are burned, are compofed of firebricks, and heated red-hot, they throw off into the room incomparably more heat than all the coals that could poffibly be put into the grate, ev n fuppofing them to burn with the greateft poffible degree of brighthels. Hence it appears that a redhot burning coal does not fend off near fo many calorific rays as a piece of red hot brick or ftone, of the fame form and dimenfions; and this interefting difcovery will enable us to make very important improvements in the conftruction of our fire-places, and alfo in the management of our fires.

The fuel inftead of being employe ed to heat the room directly, or by the direct rays from the fire, fhould be fo difpofed, or placed, as to heat the back and fides of the grate; which must always be conftructed of fire-brick or fire-ftone, and never of iron, or of any other metal. Few coals, therefore, when properly placed, make a much better fire than a larger quantity; and fhallow grates, when they are conftracted of proper materials, throw more heat into a room, and with a much lefs confumption of fuel, than deep grates; for a large mals of coals in the grate arrefts the rays which proceed from the back and fides of the grate, and prevents their coming into the room; or, as fires are generally managed, it prevents the back and fides of the grate from ever being fuficiently heated to affift much in heating the Hh 2

rouin,

room, even though they be conftructed of good materials, and large quantities of coals be confumed

in them.

It is poffible, however, by a fimple contrivance, to make a good and an economical fire in almost any grate, though it would always be advifable to conftruct fire-places on good principles, or to improve them by judicious alterations, rather than to depend on the use of additional inventions for correcting their defects.

To make a good fire in a bad grate, the bottom of the grate muft be first covered with a fingle layer of balls, made of good fire-bricks, or artificial fire ftone, well burnt, each ball being perfectly globular, and about 2 or 24 inches in diameter. On this layer of balls the fire is to be kindled, and, in filling the grate, more balls are to be added with the coals that are laid on; care muft, however, be taken in this operation to mix the coals and the balls well together, otherwife, if a number of the balls fhould get together in a heap, they will cool, not being kept red-hot by the combuftion of the furrounding fuel, and the fire will appear dull in that part; but if no more than a due proportion of the balls are used, and if they are properly mixed with the coals, they will all, except it be thofe perhaps at the bottom of the grate, become red-hot, and the fire will not only be very beautiful, but it will fend off a vaft quantity of radiant heat into the room; and will continue to give out heat for a great length of time. It is the opinion of feveral perfons who have for a confiderable time practifed this method of making their fires, that more than one-third of the fuel ufually confumed may be faved

by this fimple contrivance. It is very probable that, with careful and judicious management, the faving would amount to one-half, or fifty per cent.

As these balls, made in moulds, and burnt in a kiln, would coft very little, and as a fet of them would laft a long time,-probably feveral years,

the faving of expenfe in heating rooms by chimney fires, with bad grates, in this way, is obvious; but ftill it fhould be remembered, that a faving quite as great may be made by altering the grate, and making it a good fire-place.

In ufing thefe balls, care must be taken to prevent their accumulating at the bottom of the grate as the coals go on to confume, the balls mixed with them will naturally fettle down towards the bottom of the grate, and the tongs must be used occafionally to lift them up; and, as the fire grows low, it will be proper to remove a part of them, and not to replace them in the grate till more coals are introduced :—a little experience will how how a fire made in this manner can be managed to the greatest advantage, and with the leaft trouble.

Balls, made of pieces of any kind of well-burnt hard brick, though not equally durable with fire-brick, will anfwer very well, provided they be made perfectly round; but if they are not quite globular their flat fides will get together, and, by obftructing the free paffage of the air amongst the coals, will prevent the fire from burning clear and bright.

The beft compofition for making thefe balls, when they are formed in moulds, and afterwards dried and burned in a kiln, is pounded crucibles mixed up with moistened Sturbridge

Sturbridge clay; but good balls may be made with any very hard burnt common bricks, reduced to a coarfe powder, and mixed with Sturbridge clay, or even with common clay. The balls fhould always be made fo large as not to pafs through between the front bars of a grate.

Thefe balls have one advantage, which is peculiar to them, and which might perhaps recommend the ufe of them to the curious, even in fire-places conftructed on the best principles; they caufe the cinders to be confumed almoft entirely; and even the very afhes may be burrt, or made to disappear, if care be taken to throw them repeatedly upon the fire when it burns with an intenfe heat. It is not difficult to account for this effect in a fatisfactory manner; and in accounting for it we fhail explain a circumftance on which it is probable that the great increase of the heat of an open fire, where thefe balls are ufed, may, in fome measure, depend. The final particles of coal, and of cinder which, in a common fire, fall throug the bottom of the grate, and efcape combuftion when thefe balls are ufed can hardly fail to fall and lodge on fome of them; and, as they are intenfely hot, thefe fmall bodies, which alight upon them in their fall, are foon heated red-hot, and difpo fed to take fire and burn; and as fresh air from below the grate is continually making its way upwards amongst the balls, every circumflance is highly favourable to the ra pid and complete combuftion of thefe fmall inflammable bodies. But if thefe fmall pieces of coal and cinder fhould, in their fall, happen to light upon the metallic bars, which form the bottom of the grate,

as thefe bars are conductors of

heat, and, on account of that circumftance, as well as of their situation,-below the fire,-never can be made very hot,-any Tmall particle of fuel that happens to come into contact with them, not only cannot take fire, but would ceafe to burn fhould it arrive in a state of actual combuftion.

These facts are very important, and well deferving of the attention of those who may derive advantage from the improvement of fire-places, and the economy of fuel.

There are fome circumftances which ftrongly indicate that an admixture of incombuftible bodies with fuel, and efpecially with coal, caufe an increase of the heat, even when the fuel is burnt in a closed fire-place. No fire-place can well be contrived more completely clofed than thofe of the iron ftoves in common ufe in the Netherlands; but, in thefe ftoves,-which are heated by coal fires, a large proportion of wet clay is always coarfely mixed with the coals before they are intro. duced into the fire-place. If this practice had not been found to be ufeful, it would certainly never have obtained generally; nor would it have been continued, as it has been, for more than two hundred years.

The combination of different fubftances,-combuftible and incombuftible,-to form, artificially, various kinds of cheap and pleasant fuel, particularly adapted for the different proceffes in which the fuel is employed, is a fubject well worthy the attention of enterprifing and ingenious men. How much excellent fuel, for inftance, might be made with proper additions and proper management, of the mountains of refute coal-duft that lie ufclefs at the mouths of coal pits; and how much Hh3

would

would it contribute to cleanliness, and elegance if the ufe of improved coke, cr of hard and light fire-balls, could be generally introduced in our houfes and kitchens, inftead of crude, black, powdery, dirty fea-coal.-Of the great economy that would refult from fuch a change there cannot be the finallest doubt.

It is a melancholy truth, but, at the fame time, a most indifputable fact, that, while the industry and ingenuity of millions are employed, with unceafing activity, in inventing, improving, and varying thofe fuperfluities which wealth and luxury introduce into fociety, no attention whatever is paid to the improvement of thofe common neceffaries of life on which the fabfiftence of all, and the comforts and enjoyments of the great majority of mankind, abfolutely depend.

Much will be done for the benefit of fociety, if means can be devifed to call the attention of the active and benevolent to this long-neglect ed, but moft interefting fubject.

confequent difficulty of purfing a caufe, which feems to be fubjected to none of our fentes, has greatly restricted the progrefs of knowledge in this branch of phyfics. S me phænomena, which have long attracted the attention of the philofopher, and excited the admiration of the vulgar, have received different folutions, grounded upon as many" dif-' ferent hypothefes. No method ap. pears to have been adopted to fhew the fallacy of the one, or the verity of the other. They ftill remained as hypothefes. The following experiments, fin.ple as they are, give a folution, which carries with it ocular demonftration; and, as the juft explication of every fact is a real advance in philofophy, I truft they will not be thought unworthy of attention.

The phænomena to which I allude are thofe, which magnets, placed upon paper, exhibit with filings of iron, when they are fprinkled about them. Many ingenious men. have fuppofed, that the arrangement of the filings clearly indicated the paffage of a magnetic fluid or effluvia, in curved lines, from one pole to another of a different denomination; and hence have fought for the folution of other phænomena upon a much more extended fcale, Others, and particularly Cavallo, in his ufeful treatife on magnetilm,

action of the magnet upon

the filings, rendering each particle itself a magnet. The proper folution fprings from the following ex• periments:

Experiment I. Place an artificial magnet, of the ufual oblong form, and of fufficient ftrength, upon a difh; let the ends be two or more inches diftance from the edge or rim: cover the magnet with water about

ones