Good barilla

Rough Effex potash, the very beft

7

5

He also mentions that the average price of barilla, for three years paft, was twenty-feven pounds ten fhillings per ton.

We fear, that unless the Bombay alkali could be afforded at a lower rate than Mr. Scott mentions, it has little chance of becoming an article of commerce to this country.

We have heard of a kind of foap that is manufactured in India, which may be employed in washing with fea water, with the fame effect as common foap has with good foft water. It would be a matter of fome importance to a maritime and commercial nation to have the nature of this compofition afcertained.

POLITE ARTS.

Mr. William Yates, furveyor, having, at his own expence, made a new furvey of the county of Lancafter, and prefented a copy of it, with an atteftation of its accuracy by a confiderable number, of the inhabitants of that county, obtained the Society's premium.

MANUFACTURES.

Under this head, Mr. Thomas Greaves, near Warrington, tranfmits to the Society fome fpecimens of paper made from the bark of withens, i. e. willow twigs. The bark was ftripped from the twigs in autumn, which must have been attended, we fhould think, with a confiderable expence. Had they been pulled off in the month of April, juft after the fap begins to flow, as is commonly done by those who carry on the business of fine basket-making to a great extent, it could have been done at a much smaller charge.-As great quantities of this bark are thrown away as entirely useless, it would feem that it might furnish materials for a confiderable quantity of paper, at a very low price. For Mr. Greaves has proved experimentally, that it can be easily converted into paper without any addition-and that it is by no means neceffary it fhould either be previously dried, or freed from its leaves, before it be applied to that use. We fhould think hop binds would answer this purpose still better.

We have here fome farther atteftations of the goodness of English-made paper for the purpofe of taking impreffions from copper plates, fo that, it is probable, this branch of manufacture will foon be fully eftablished in Great Britain.

As it appears probable that the breeding of filk worms may in time be introduced into this country, the Society beftow a due degree of regard to every obfervation that may tend to give ufeful information on this point. In the prefent volume, the public are favoured with an intelligent letter on that subject from Mr. Peter Noaille, of Greatnefs, Kent. It relates to the proper mode

mode of winding off filk from the cocoons. It ftates, that if a thread be formed of 18 or 20 cocoons, the value of fuch filk may be eftimated at 20 fhillings per pound, of 16 ounces, while a pound of filk compofed of the very fame materials, confifting of only fix or eight cocoons, would be worth 30 fhillings; and if four or five cocoons only, it might vie with the moft fuperlative produce of Italy, that would be worth 40 fhillings per pound. He then eftimates the expence at which this fuperior fort may be obtained. With this view, he ftates that one woman and a girl can eafily wind off one pound of filk, of the finest quality, in a day; and that the fame woman and girl could wind, of the coarfeft fort of filk, fix, eight, or more (lay ten) pounds in a day. Let the wages of the woman and her girl be ftated at one thilling per day.

The cost of winding 10 pounds of filk of the finest fort, would therefore be

The price of it at 40 fhillings per pound

Net price

The coft of winding 10 pounds of the coarfeft fort would be

The price of it at 20 fhillings per pound

O 10 0 20 0 0

Net price

9 19 0

So that the profit by winding it off fine would be 9 An attempt had been made to spin the filk directly from the cocoons, without having been previoufly reeled, which he shews to be, in all circumftances, a very un-ceconomical practice.

MECHANICS.

Under this head, we find a defcription of a new machine for meafuring angles, invented by Mr. Matthew Hill, of Scarborough. A sector, and tool for letting wheels and pinions in watch work, invented by Mr. Jofeph Ridley.-And a carriage for conveying timber over foft or boggy land, by Mr. Joha Befant, Weftminster; of none of which can we convey an accurate idea, without the plates.

The volume concludes with the ufual lifts of rewards beflowed-prefents received-premiums propofed, and the prefent members of the Society.

An.....n.

ART.

ART. V. Experiments and Obfervations on Animal Heat, and the Inflammation of combuftible Bodies: Being an Attempt to refolve the Phenomena into a general Law of Nature. By A. Crawford, M. D. F. R. S. L. & E. and Member of the Philofophical Socie ties of Dublin and Philadelphia. The Second Edition, with very large Additions. 8vo. 7s. Boards. Johnfon. 1788.

THE

HE_theory of animal heat and combuftion, as delivered by Dr. Crawford in the former edition of his work, is now more fully eftablished by the refults of many new experiments which appear to have been made, with the moft fcrupulous attention to accuracy, in order to afcertain fome new facts, and to correct fome miftakes in the conclufions drawn from thofe that were before prefented to the public.

It feems now to be the prevalent opinion, that experiments, and inductions from them, are the only means by which we are permitted to interpret the characters impreffed by the Deity on his works; and the philofopher, who is thus employed in cultivating natural knowlege, is well aware that this method of fearching after truth, neceffarily demands much labour, and patient investigation, aided by fagacity, and directed with judg

ment.

Dr. Crawford pleads, in excufe for the late appearance of this fecond edition (containing new difcoveries, and the correction of errors), the difficulty in purfuing, and the time requifite for making, experimental refearches. He is convinced, as indeed every true philofopher must be, that to correct errors is the beft method of apologizing for them; and that though the free communication of difcoveries is effential to the progrefs of knowlege, yet it is of much greater importance to the interefts of science, that facts fhould be well afcertained, than that they fhould be fpeedily published. He does not, however, mean to infinuate that the facts which he has now fubmitted to the public are free from error; miftakes may eafily arise in every attempt, where fo much nicety is required, to determine the relations between the fubtle elements of fire and air; and he hopes, that fuch of them as may be found in his work, will, by the candid public, be afcribed to the imperfections of our fenfes, or the inftruments employed in the courfe of the experiments.

The abftrufenefs of the fubject, and the novelty of Dr. Crawford's theory*, were probably the reafons why his doctrine met with fome oppofition, on its firft appearance; especially by Mr. Morgan +, who made many pertinent reflections on Dr. Crawford's opinions. As an amicable contention, fuch as Mr. Morgan's with Dr. Crawford really was, always promotes science,

For an abridgment of which fee Rev. vol. lxi. p. 378. + See Review, vol. lxiv. p. 350.

we

we hoped that the Doctor would be incited to repeat, diverfify, and extend his experiments. This he hath now done, and his theory, not materially altered, has received much additional fupport.

As we have before given an abstract of our ingenious Author's theory of animal heat, and of the inflammation of combuftible bodies, it is unneceffary that we should repeat it. We fhall therefore only endeavour to refresh the memory of our readers, by informing them that according to the refults of Dr. Crawford's experiments, it appears that pure air, containing a large portion of elementary fire, is, by infpiration, received into the lungs; and that the blood, impregnated with phlogifton, is returned from the extremities. Now the attraction of air to phlogifton being greater than that of blood, the phlogifton quits the blood, and unites with the air; the air at the fame time depofiting part of its elementary fire: and the capacity of the blood for receiving heat being increased by the change it undergoes in lofing its phlogifton, the elementary fire before depofited by the air will be abforbed by the blood. The blood in its paffage through the capillaries is again impregnated with phlogifton, in confequence of which, its capacity for heat is diminished, and therefore, in the courfe of the circulation, it will give out, and diffufe over the whole fyftem, the heat acquired in the lungs: or, in a word, in refpiration, the blood is continually discharging phlogiston, and absorbing heat, and on the contrary, during its circulation, it is continually imbibing phlogifton, and emitting heat.

With refpect to the inflammation of combuftible bodies, it appears, by Dr. Crawford's experiments, that when atmofpherical air is converted into fixed air and aqueous vapour, a great part of its heat is detached: it appears alfo that the capa cities of bodies for containing heat are increased by parting with their phlogifton in the process of combuftion. Hence in the act of inflammation, the phlogifton that is feparated from the inflammable body unites with the pure air, which, at the fame time, being converted into fixed air, and aqueous vapour, gives off a large portion of its abfolute heat; this abfolute beat, thus extricated, produces an intenfe degree of fenfible beat, and if the extrication be fudden, the heat will burst forth into flame.

The explanation which this theory affords to the feveral phenomena attendant on animal heat, and combuftion, is a strong confirmation of its truth, independently of the eafy folution which it gives of a great variety of facts. The phyfiologift will here find fome of thofe parts of the animal economy explained which hitherto have been unaccounted for: the natural

philofopher and chemift will also find many facts elucidated which could fcarcely be folved, on any other hypothefis.

With respect to the nature of heat, whether it be a fubflance or a quality, our Author's doctrine is totally unconnected with any hypothefis concerning it, being founded on this fimple fact deduced from experiment, viz. that the changes which are produced in the temperatures of different bodies by the application of given quantities of heat, are different. He has, indeed, in many places, ufed expreffions which feem to favour the materiality of heat; but his fole motive for adopting fuch language was, as he fays, because it appeared more confonant to the facts which he had established by experiment. He is nevertheless perfuaded that it will be extremely difficult to reconcile many phenomena with the fuppofition that heat is a quality. It is not eafy to comprehend on this hypothefis, how heat can be abforbed in the procelles of fufion, evaporation, or combuftion; or how the quantity of heat in the air can be diminished, and that in the blood increased, by refpiration: but the opinion that heat is a dif tinct fubftance, or an element fui generis, being adopted, the phenomena admit an eafy and obvious interpretation. Fire, the Doctor thinks, will, on this fuppofition, be confidered as a principle which is diftributed in various proportions throughout the different kingdoms of nature; he fuppofes the mode of its union with bodies, to refemble that particular fpecies of chemical union, wherein the elements are combined by the joint forces of preffure and attraction, fuch as the combination of fixed air with water. If, however, fire be a fubftance, fubject to the laws of attraction, the mode of its union with bodies feems to be different from that which takes place in chemical combinations; for in thefe, the elements, as Dr. Crawford obferves, acquire new properties, and lofe thofe by which they were characterized before the union: but he has fhewn that fire does not, in confequence of its union with bodies, lofe its diftinguishing properties; confequently, we have no direct proof of its materiality. Dr. Crawford's conclufions are, however, as we hinted above, not in the leaft affected by the nature of heat or fire; they are fimply the facts refulting from experiments and the testimony of the fenfes, and they must be admitted notwithstanding any adopted hypothefis. The fubject is, doubtlefs, extremely intricate; and much time, a long feries of accurate experiments, and the most minute obfervations, are perhaps ftill requifite to complete the investigation of the nature of this fubtle principle. Few years, indeed, have elapfed, fince philofophers have turned their attention, in a proper manner, to the fubject; and from the progrefs that is already made, we may hope that a few more years will unfold what is now wrapt in obfcurity, or involved in error.

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