will abforb and carry back part of the electric fire to the refervoir from whence it was extracted.

If these conjectures be true, to excite an electrical machine effectually, we must,

Ift, Find out thofe parts of the cushion which are preffed by the glafs of the cylinder.

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2. Apply the amalgama only to those parts.

3 Make the line of contact between the cylinder and cushion as perfect as poffible.

4. Prevent the fire that is collected from efcaping.

About the year 1782, I applied a loofe flap of leather to the front of the cushion; the amalgama was fpread over the whole of the flap; the cushion was then put in its place, and the loofe flap of leather doubled down, or rather turned in, more or lefs, till by fucceffive experiments the fituation was difcovered which produced the greateft effect; for, by this means, the quantity of amalgama acting against the cylinder, was leffened. I was naturally led to contract the breadth of the cushion, and place it in fuch manner that it might be easily raised or lowered.

The advantages gained by this method were confiderably improved by a very ingenious gentleman. He glued a bit of leather on a large piece of cork, and placed his amalgama on the leather; with this he rubbed that zone of the glafs cylinder which bears against the cufhion. By this excellent contrivance, the line of contact between the cylinder and cushion is rendered very perfect, the fmaller pores of the glafs are filled with the amalgama, and the fuperfluous parts of it are depofited on the cushion.

Beccaria fuggefts, that the amalgama thus depofited on the furface of the glafs forms a continued feries of conducting particles, which carry the fire to the prime conductor, and, under certain circumflances, back again to the cushion.

Another ingenious electrician ascertains the line of contact formed between the cylinder and cushion, by placing a line of whiting, which has been previously diffolved in fpirits of wine, on the cylinder on turning the cylinder, this whiting is depofited on the cufhion, and marks the places which bear against the cylinder. The amalgama is to be placed only on those parts which are marked by the whiting.

Either of thefe modes will fucceed. If the firft is ufed, no amalgama is to be placed on the cushion; that which is rubbed into the cylinder, and depofited by it on the cushion in its revolutions, will produce an aftonishing quantity of fire. In either method, when the cylinder is rubbed with the amalgamated leather, that part of the oil, or black filk which lies above the cushion, is to be turned back; and if by accident any particles of the amalgama ftick to it, they must be wiped off carefully.

If the electricity of the cylinder grows lefs powerful, it is easily renewed by turning back the filk which lies over it, and then rubbing the cylinder with the amalgamated leather.

A very fmall quantity of tallow placed over the amalgama, is obferved to give more force to the electric powers of the cylinder."

The

The small tract on magnetifm is here annexed, merely to illuftrate the use of an apparatus, conftructed in order to exhibit the general phænomena of that fubtle agent. It is given as an extract of a larger work, which is laid afide for the prefent, and actually contains nothing new.

Among a few errata, not noticed in the table, we must particularly point out one in p. 135, 1. 13, where the letter of reference a is put inftead of d, fince it affects the fenfe of the paffage fo materially as to render it unintelligible to beginners.

We are aware, that philofophical writers, who are more intent upon matter than words, claim a right of exemption from elegance of style; but grammatical accuracy is, in our opinion, what no writer of any clafs can be allowed to dispense with. We do not mean to tax Mr. A. in particular with omiffions of this nature, for men of great name, and who had better write any how, than not write at all, have often offended us in this respect. What we here particularly allude to, is, the very frequent false conftruction of the indicative mood with conditional adverbs or conjunctions, fuch as in the above quotation, If the firft is ufed' and elsewhere, If two tubes are fufpended,' Whether the conductor is infulated or not.' In all which inftances the conjunctive be is no doubt the proper mood of the auxiliary.

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ART. VIII. Flora Dietetica: or, Hiftory of Efculent Plants, both Domeftic and Foreign. In which they are accurately defcribed, and reduced to their Linnæan generic and fpecific Names. With their English Names annexed, and ranged under Eleven general Heads; viz. Efculent, 1. Roots; 2. Shoots, Stalks, &c.; 3. Leaves ; 4. Flowers; 5. Berries; 6. Stone fruit; 7. Apples; 8. Legumens; 9. Grain; 10. Nuts; 11. Funguses. And a particular Account of the Manner of using them; their native Places of Growth; their feveral Varieties, and phyfical Properties: together with whatever is otherwise curious, or very remarkable in each fpecies. The whole fo methodized, as to form a fhort Introduction to the Science of Botany. By Charles Bryant, of Norwich. 8vo. 6s. boards. White. 1783. T is fo common a propenfity in the ignorant to decry and ridicule parts of knowledge with which they are unacquainted, that we need not wonder at the imputations of frivolousness and inutility, which many have fo freely beftowed on the delightful fcience of botany. At the fame time, its friends may boldly affert, that abundant proofs are continually appearing of its extenfive importance, and real refpectability; and in particular, the Linnean fchool, who have been peculiarly charged with converting the whole ftudy into a fyftem of words and trifles, have been moft diligently engaged in applying their refearches to purpofes of public benefit. That invaluable collection of effays on various fubjects in natural hiftory, the Amanitates Academice of

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the Upfal University, contains many admirable examples of this application of science to matters of confeffed utility; and we may particularly mention thofe entitled Flora Oeconomica, Planta Efculenta, Acetaria, Macellum Olitorium, and Fructus Efculenti, as connected with the subject of the work now before us.

Mr. Bryant (who lately gave a specimen of his accuracy in botanical description, by a minute account of two fpecies of Lycoperdon *) has aimed, in the present volume, to give a clear and intelligible, though concife, account of all the known plants ufed by various nations as articles of diet. He has arranged them under diftinct heads, as mentioned in the titlepage; fixed the genus and fpecies, by annexing the Linnæan name; given a brief description of all except the most common and univerfally known; and fubjoined the fenfible qualities, ufes, modes of preparation, &c. of each article. As fuch a work muft be, for the most part, merely a compilation, fidelity, and clearness in defcription, and judgment in felection, are the qualities alone requifite for its completion; and in these our Author does not appear deficient. From his ftyle, and the unvaried limits of his matter and manner, we cannot indeed conclude him to be a person of enlarged education, or extenfive acquirements; but, as far as he goes, he may probably be safely trufted; and his work is well calculated for the information and instruction of the generality of readers. Here are many facts refpecting the dietetical ufes of vegetables common amongst us, which will be new to most readers, and well deserve to be known. In this country, it is true, we are not much difpofed to seek for luxuries in the fields and woods; though it would be better for our conftitutions, and perhaps, too, for our morals, were such a tafte more encouraged.

What we chiefly regret in the prefent performance, is the want of a proper union of chemical with botanical knowledge. The principles and conftituent parts by which vegetables are rendered fit articles for the food of man and other animals, are only to be difcovered by the application of tefts belonging to chemistry; while botany ferves to ascertain the identity of the fpecies in which fuch qualities have been difcovered; and, fometimes, analogically, to difcover them in others. Scarcely any thing would be more curious and useful, than an enquiry into the nature of all the various dietetical articles, conducted by a man of real science, on the conjoined principles of chemiftry and natural hiftory.

See Monthly Review for October 1783.

ART.

ART. IX. Doctrines and Practice of Hippocrates in Surgery and Phyfic; with occafional Remarks. By Francis Riollay, M. B. 8vo. 5s. boards. Cadell. 1703.

HE purpofe of this writer is explained in the following

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comparison, or rather contraft, between his work and the elaborate performance of the celebrated Le Clerc. • The main object of his, as an hiftorian, was to reprefent, in a gene-. ral manner, the state of phyfic in the time of Hippocrates. The main object of mine, is to enquire, by entering into greater particulars, how far a ftudy of his writings is ufeful at prefent; and, at the fame time, by freeing them, in a great measure, from the unneceffary minutenefs, frequent obfcurities, contradictory paffages, endless repetitions, and confused manner [matter?] with which their worth is mingled and disfigured; to fpare to others a good part of the labour I once thought myself bound to undergo. His provincé was confined to facts; mine extends to opinions: in one word, to examine impartially whe ther the cause is equal to the effect; or whether the facts deferve the opinions they have occafioned, is the object of this attempt.

That the flight sketch this Author has given, or rather the felection he has made, of the works of Hippocrates, will convey an adequate idea of all his facts and opinions, we can by no means admit. It may, indeed, abridge the ftudent's labour, by convincing him that the writings of this venerated fage are not at all worthy the expence of time and labour requifite for their ferious perufal; a conclufion that the fpecimens here exhibited may be thought too juftly to warrant. Indeed, we can scarcely forbear to cry" Procul, procul efte profani!" and to complain of our Author for removing a veil, which has concealed the nakednefs of antient phyfic for upwards of two thousand years. It is certain, that how refpectable foever many of the Hippocratic doctrines may appear in their Greek robes; they make but a contemptible figure in a plain English garb. We are not dif pofed to indulge our Readers in general with a laugh at the expence of this reverend fire of phyfic, and therefore forbear to quote fome of the most remarkable paffages tranflated by the Writer before us. He is, indeed, by no means guilty of the usual fault of tranflators and annotators, too partial an attachment to their author; for his remarks are drawn up in a very free ftyle; and he does not fcruple every where to inculcate the proper diftinction between the refpect perfonal v due to the father. of phyfic, and a fuperftitious reliance on opinions formed in the very infancy of the art itself

The general mode in which Dr. Riollay has proceeded in this performance, is, to give two or three chapters-literally tranf

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lated, or abridged, from the original, and then to fubjoin fome of his own obfervations on them. These obfervations are, for the most part, fenfible and candid; and though, as we before faid, we cannot allow that a complete view of the matter contained in the voluminous works of Hippocrates, can be given in fo small' a compafs; we acknowledge, that a competent notion of his general doctrine and its merits, may be derived from this publication. It will therefore be an ufeful prefent to the ftudent; informing him, in an eafy and compendious way, of things with which he ought to have fome acquaintance, and yet which by no means deferve the time and labour frequently beftowed upon them. The number of chapters is twenty-four. The most confiderable of the Author's own effays, is that on the fubject of critical days; in which he principally aims at a refutation of Dr. Cullen's theory of this matter. We believe the very ingenious profeffor has made fewer converts in this point, than in most of his other fpeculations; notwithstanding he has fo modified the Hippocratic doctrine, and admitted fo many exceptions, that his opinion is neither any great fupport to the Grecian oracle, nor any rule in practice.

In his conclufion, Dr. Riollay expofes, in a lively manner, the very extravagant and injudicious praifes beftowed on Hippocrates by M. Diderot, and printed in the celebrated French Encyclopedie.

ART. X. Plays of Three Acts; written for a private Theatre. By William Hayley, Efq. 4to. 1 25. boards. Cadell. 1784.

F

ROM the fertile and amufing pen of Mr. Hayley, we here receive a volume in quarto, containing five plays, viz. two tragedies, and three comedies, each in three acts. The comedies are in rhime,-ftart not, Reader! in rhime-but fuch rhime, fo familiar, fo eafy, fo flowing, that profe itself can scarcely appear more natural, more convenient for the purposes of diaJogue, or the bufinefs of the drama. Like the ancient lambic, recommended by Ariftotle, and characterifed by Horace, as the meafure peculiarly fuited to the fcene-Natum rebus agendis.

Think not, however, learned and judicious Reader! that we mean to authorife rhime, as the general vehicle of comic dialogue; or to confirm the doctrine countenanced by the Preface of the ingenious writer, whofe new publication now lies before. us. We only accede to the conclufion of that Preface, allowing that all works, excellent in their kind, fhould be received with indulgence and approbation. Measure in comedy,-not rhime indeed, but familiar blank verfe-is to this day agreeable to the public ear in the plays of Beaumont and Fletcher, Johnson and Shakespeare. Rhime too, in the plays of Hayley, may not only J

be