ART. II. Experiments and Obfervations on a new Species of Bark, fhewing its great Efficacy in very fmall Dofes: alfo, a comparew of the Powers of the Red and Quilled Bark; being an Attempt towards a general Analysis and compendious Hiftory of the valuable Genus of Cinchona, or the Peruvian Bark. By Richard Kentish, M. D. Member of the Royal Medical Society at Edinburgh, Correfpondent Member of the Society of Scottish Antiquaries, &c. &c. 8vo. 2s. 6d. ftitched. Johníon. London, 1784. THE HE analyfis of the Peruvian bark has been profecuted with much industry by several medical writers; but, as happens in the greater part of experimental inquiries, the refult of the investigation has not been uniformly the fame. Few men, comparatively, having either leifure or inclination for fuch refearches, the opinion of the faculty is, in general, formed upon the authority of the most eminent, or frequently, the latest inquirer; whofe decifion continues to be refpected as the standard of truth, until experiments, apparently more accurate, fhall give rife to the establishment of new facts. The refult of the experiments made by the author now before us on the cinchona officinalis, differs, in fome particulars, from that which has been deduced by Dr. Percival. The latter has faid, that the Peruvian bark, and many other vegetable bitters and aftringents, yield their virtues as perfectly to cold as boiling water. But Dr. Kentish contends, from his own experiments, that though the aftringent principle of the bark be beft extracted by cold water, the bitter principle, or that which refides in the refinous part, is obtained most effectually by coction; and he denies the obfervation afferted by Dr. Percival, that as much of the refin of the bark is diffolved by cold maceration as by coction. He thinks that the bitter taste of the decoction, compared with the infufion, fufficiently invalidates this remark; but the decoctions of the Red and Caribbæan bark put it beyond all doubt, in his opinion, that the bitter principle is more copiously yielded by coction than cold infufion. In the fubfequent chapter the author relates his experiments on the red Peruvian bark, which was lately fo much extolled for its fuperior virtues by Dr. Saunders. According to Dr. Kentish, the quilled bark invariably yields more gummy or watery extract than the red, and the latter more fpirituous or refinous extract. He therefore admits, that it may be preferable to the quilled in fome inftances, though not, not, as Dr. Saunders fuppofed, by its fuperior aftringency, but rather on account of its bitternefs. This remark we think well founded; and as we know from experience that fome intermitting fevers are beft cured by bitters, while others, on the contrary, can only be overcome by aftringents, the different opinions which have been entertained respecting the fuperior efficacy of thefe two fpecies of bark, are reconcileable with juft obfervation, In fome cafes the red kind, and in others the quilled, may prove the moft fuccessful medicine. Much, however, muft depend upon the ftate in which it is adminiftered. One of Dr. Kentifh's experiments clearly proves the fuperior aftringency of the common bark. To two ounces of the decoction of red bark he added ten drops of the tincturamartialis. A purple colour was produced, very different from the inky blacknefs obferved in other experiments, and the liquor continued long without letting fall any precipitate. After standing twenty-four hours it fcarcely could be faid to be of a black colour. "It is to be wished," fays the author, That Dr. Saunders had given us an experiment of this kind; it is one which manifefts at once the fuperior aftringency of the common bark, and explains the nature of the aftringent principle. The decoction abounds more in refin than the infufion; yet, on the addition of chalybeates, it manifefts lefs aftringency. The conclufion is plain; the refin is not the aftringent, but the bitter principle. Dr. Saunders, indeed, is not the first author who has mistaken this matter. The ingenious Dr. Lewis fays, The aftringency of the cortex refides wholly in its refin, which is not foluble in watery li quors." Neumann's Chem. p. 399, note. Dr. Percival long ago detected this error; and we cannot help being rather furprised that Dr. Saunders fhould not have been acquainted with this discovery, as he speaks of the doctor in terms of respect due in fo accurate a writer, and has taken the 8th experiment from his works. We fhall here fubjoin two experiments, which prove, beyond a doubt, the truth of the remark that the gum is the aftringent prin. ciple. Exp. 1. One fcruple of the refinous extract of bark was diffolved in one ounce of diftilled water. To the mixture were added gtt. v. of the tinct. martial. The liquor immediately became of an inky black colour, greatly fuperior to that produced by the following, Exp. 2. One scruple of the refinous extract of bark was diffolved in one ounce of rectified spirit. To the mixture were added gtt. v. of the tinct. flor. martial. A black celour was produced, but greatly inferior to that produced by the preceding experiment.' The fubfequent part of the treatise relates to a new species of bark, evidently of the genus of cinchona, produced in the inland of St. Lucia, and diftinguished by the name of the Caribbean bark. It appears, from Dr. Kentifh's experiments and obfervations, that this is greatly fuperior to the other fpecies of bark, both in point of aftringency and bitternels; and there is no doubt of its being the fame with what is defcribed by the French writers, particularly Mr. Mallet, as being indigenous in Martinique and Guadaloupe. This bark is faid to be more abundant than either of the former fpecies in aftringent gum, and bitter refin, and to be a very active remedy in all thofe diseases which require the ufe of the cinchona. This fpecies of bark proves emetic in maller dofes than might be expected; but Dr. Kentish fays that he finds the dofes of five, eight, or ten grains, repeated at thort intervals, produce all the good effects of the largest dofe of common or red bark. In fome cafes we have been fatisfied with its fuperior efficacy. But it feems to be beft adapted to ftrong conftitutions; and even in these it ought to be joined with a few grains of the fpecies aromatica, or fome fuch medicine, to make it fit easier upon the ftomach. It will be a valuable acquifition should the Peruvian bark, as has been afferted, be fuffered by the Spaniards to decline. ART. HI. A Collection of Original Royal Letters, written by King Charles the First and Second, King James the Second, and the King and Queen of Bohemia; together with original Letters written by Prince Rupert, Charles Louis Count Palatine, the Duchefs of Hanover, and feveral other diftinguished Perfons; from the Year 1619 to 1665. Dedicated, with Permillion, to his Majesty, by Sir George Bromley, Bart. Illuftrated with elegant Engravings of the Queen of Bohemia, Prince Rupert, Emanuel Scrope Howe, and Ruperta, natural Daughter of Prince Rupert; and a Plate of Autographs and Seals. 8vo. 10s. boards. Stockdale. London, 1787. THESE letters were written by fome of the most diftin guished perfonages of the last century. They came into the poffeffion of Sir George Bromley, Bart. in confequence of his being defcended from Ruperta, natural daughter to Prince Rupert, third fon of Frederic King of Bohemia, and nephew to Charles the First, King of England. As the greater part of the letters contained in this collection were written by the Palatine family, or addreffed to them, Sir George Bromley gives an account of that family, in or der to explain the facts and circumftances referred to in thefe those letters. The following account of Prince Rupert, from whom the editor of this collection is defcended, con tains fome particulars that illuftrate the progress of the arts, and are interefting to the republic of letters. • After the restoration Prince Rupert was invited to return to England, and had feyeral offices conferred on him. On the 28th of April 1662, he was fworn a member of the privy-council; and, in December following, he was admitted a fellow of the royal fociety. In the year 1666 the king entrusted him, in conjunction with the Duke of Albemarle, to command the fleet; when he exhibited all the qua. lities that are neceffary to conftitute a great admiral. By his happy return to the fleet, on the 3d of June, he wrefted from the Dutch the only victory they had the appearance of gaining; and afterwards, on the 24th of the fame month, he beat them effectually, purfued them to their own coaft, and blocked up their harbour. Indeed, the great intrepidity which Prince Rupert difplayed in this naval war, was highly and justly celebrated in his own time; and, in the laft Dutch he feemed to retain all the activity and fire of his youth, and beat the enemy in féveral engagements. war, • From this time Prince Rupert led a quiet, and chiefly a retired life, moftly at Windfor-Caftle, of which he was governor; and he very much employed himself in the profecution of chemical and phi lofophical experiments, as well as in the practice of mechanic arts, for which he was very famous. He is mentioned by foreign authors with applause for his skill in painting; and is confidered as the inventor of mezzotinto, of which he is faid to have taken the hint from a foldier scraping his rufty fufil. The circumstances are thus related: The prince going out early one morning, obferved a centinel at fome diftance from his poft, very busy doing fomething to his piece. The prince asked what he was about? He replied, that the dew had fallen in the night, had made his fufil rufty, and that he was scraping and cleaning it. The prince, looking at it, was ftruck with fomething like a figure eaten into the barrel, with innumerable little holes clofed together, like friezed work on gold or filver, part of which the foldier had fcraped away. From this trifling incident Prince Rupert is faid to have conceived mezzotinto. He concluded that fome contrivance might be found to cover a brass plate with fuch a grained ground of fine preffed holes, which would undoubtedly give an impreffion all black; and that, by fcraping away proper parts, the smooth fuperficies would leave the reft of the paper white. Communicating his ideas to Wallerant Vaillant, a painter whom he maintained, they made feveral experiments, and at last invented a steel roller, cut with tools to make teeth like a file or rafp, with projecting points, which effectually produced the black grounds; thofe being fcraped away, and diminished at pleasure, left the gradations of light. It is faid, that the firft mezzotinto print ever published was executed by his highnefs himself. It may be feen in the first edition of Evelyn's Sculptura;" and there is a copy of it în the fecond 66 edition, printed in 1755. • Prince Prince Rupert alfo delighted in making locks for fire arms, and was the inventor of a compofition calicd, from him, Prince's Metal, and in which guns were caft. He communicated to the Royal Society his improvements upon gunpowder, by refining the feveral ingredients, and making it more carefully; by which, as appeared by feveral experiments, its force was augmented, in comparison of ordinary powder, in the proportion of ten to one. He likewife ac quainted them with an engine he had contrived for raifing water; and sent them an inftrument, of which he made ufe, to cast any platform into perspective, and for which they deputed a felect committee of their members to return him their thanks. He was the inventor of a gun for discharging feveral bullets with the utmoft fpeed and facility; and was the author of fundry other curious inventions. He died at his houfe in Spring-Gardens on the 29th of November, 1682.' The hiftorical or political information contained in these letters is not very confiderable. Facts are feldom placed in a new light, or characters illuftrated, by incidents or anecdotes that are not recorded in the general history of the age. At the fame time, as they were written by perfons of the higheft ftation, and who had themselves a perfonal share in great and important tranfactions, they will gratify that numerous clafs of readers who are attached to the study of biography and antiquities, and who wish to furvey or criticife the private and unaffected walks of majefty. The engravings, by Sherwin, which accompany this work, are elegant in a high degree; that of Prince Rupert in particular, which fronts the title-page, indicates the hand of a master in the art. ART. IV. The Fane of the Druids; a Poem. 4to. 2s. 6d. ftitched. Murray. London, 1787. THE fubject and plan of this poem were fuggefted to the author by his having feen a small druidical fane. This monument of remote antiquity brought to his view a race of men whofe manners and rites are interefting to curiosity, and pleafing to the imagination. As the druids committed none of their inftitutions or discoveries to written records, and as the ancient hiftorians who make mention of them were not initiated in their mysteries and fecrets, the hiftory of druidifm is involved in impenetrable darkness. By comparing the accounts of the ancients on this fubject, and felecting what is moft probable in their defcriptions, our author has reared the fabric of this elegant poem. It begins with a defcription of the manners and habitations of the |