more beneficial to the bookfellers than to the public. That line of reading nourishes vanity, and has a tendency to enfeeble the mind.

The work now under confideration is liable to these objections; but thould it excite a defire for natural knowledge, it may be useful in preparing for the perufal of fyftematic treatises. An abridged view of natural hiftory, divefted as much as poffible of technical terms, and clothed in a becoming drefs, would prove a moft acceptable present to our youth of both fexes. It would open their minds, ripen their judgment, and ftrengthen their memory; and it would furnish an exhauftlefs fund of entertainment and inftruction from the animated fcenes with which they are furrounded.

The editor's preface has the air of hafty and careless compofition. He adopts many of the fentiments of Rouffeau, and ftrongly recommends that children fhall be exercised in defcribing external objects. The choice which he has made of materials is, on the whole, judicious. We with, however, that he had borrowed lefs from the Spectacle de la Nature, a work almost out of date. We must particularly object to the article on Becs, that on Fishes, and that on Fofils. Thefe extracts betray an ignorance of optics and chemistry, and advance opinions which have long been exploded.

ART. III. Philofophical Transactions of the Royal Society of London, Vol. LXXXI. For the Year 1791. Part II. pp. 290. 4to. 8s. 6d. fewed. Elmfley. London, 1792.

[ Concluded. ]

Art. VIII. ON the Rate of Travelling, as performed by

Camels; and its Application, as a Scale, to the Purposes of Geography. By James Rennel, Efq. F. R. S.This excellent geographer begins his paper by paying a handfome compliment to the Affociation for promoting Discoveries in the interior Parts of Africa.' Under the patronage of that generous and humane fociety, he trufts that this vaft region will at length be explored, and the latitude and longitude of the remarkable places ascertained by astronomical observations. In the mean time, he recommends it to travellers to take the bearings with pocket-compafs, and to note the time elapsed between each ftation; for the rate of a camel's movement,'.he remarks, is, beyond all others, the leaft variable.' To establish this interefting point, he has, with his ufual accuracy, examined and compared three different journals: that of Mr. Carmichael, who

traverfed

traversed the Great Defert in the year 1751; one kept by Colonel Capper in 1778; and the third by Mr. Hunter in 1767. The first gentleman travelled from Aleppo to Rackama in 204 hours and 20 minutes; the second in 205 hours and, 44 minutes; and the third in 197 hours and 30 minutes. Their rates of travelling were therefore as follows: Mr. Carmichael's 2,475 British miles an hour; Colonel Capper's 2,51; and Mr. Hunter's 2,585 fo that the average may be ftated at 21⁄2 miles an hour. Light caravans travel about nine hours each day, and heavy caravans 7 hours. They halt generally one day in twelve. A light camel travels at least one fifth fafter than one carrying a load of five or fix hundred pounds. Mr. Rennel's computations are illuftrated by a sketch of the routes across the deferts from Aleppo to Bufforah.

Art. IX. On Infinite Series. By Edward Waring, M. D. F. R. S. Lucasian Profeffor of Mathematics in the University of Cambridge.The forbidding afpect of this paper prevents us from entering into any minute examination of it. Dr. Waring gives a concise hiftory of the discoveries in infinite feriefes, makes fome miscellaneous remarks of fmall importance, and refers perpetually to his Meditationes Analytica.

Art. X. An Account of fome Appearances attending the Converfion of caft into malleable Iron. In a Letter from Thomas Beddoes, M. D. to Sir Jofeph Banks, Bart. P. R. S.Dr. Beddoes adopts the opinion of the French chemists, that caft iron contains a mixture of the oxyd or calx of that metal, together with plumbago, or the compound of charcoal and iron. But though he leans ftrongly to the chemical theory of M. Lavoifier, he differs from that ingenious philofopher with regard to the conftitution of charcoal. Inftead of admitting this to be a simple substance, he afferts that it confifts of hydrogene and azote, or of the bafes of the inflammable and phlogisticated gafes. Whether this deviation from the fyftem of M. Lavoifier be judicious, we shall not venture to decide; but we entirely agree with Dr, Beddoes that the exploded doctrine of phlogiston is unable to explain the phenomena which he describes.

As the reverberatory has lately been fubftituted for the finery furnace, in the iron manufactories, the procefs of converting caft into malleable iron admits of infinite variations. Dr. Beddoes had an opportunity of obferving the appearances which the metal puts on during that change. In fomewhat more than half an hour the charge was nearly melted, and the workman began to ftir the liquid mafs. It foon heaved, and emitted a blue lambent flame. This was called fermentation. In half an hour the blue flame broke out over the whole mafs, which feemed to grow hotter, and the motion was general. In an hour the

F 4

conftant

conftant stirring had reduced the metal to the appearance of fine fand, and the flame had grown more dilute. The mafs was now heated, and a hiffing noise heard. About two hours from the commencement of the operation, the finery cnider boiled up. The metal was now gathered into lumps, and brought to the hottest part of the furnace, where it was fufed in fix or eight minutes.

The heaving or fwelling motion,' fays Dr. Beddoes, fo confpicuous in the process, is doubtlefs owing to the discharge of an elastic fluid; and the lambent deep blue flame, breaking out in spots over the whole furface, fhews that this elastic fluid is an inflammable gas of the heavy kind.' He explains, from his own principles, the production of this heavy inflammable air, in the following manner: The oxygene of the imperfectly

reduced metal combines with the charcoal to form fixed air; • at the fame time another portion of the charcoal is thrown into an clastic state; that is, into inflammable air, and burns on ⚫ the furface with a very deep blue flame, on account of the ad• mixture of fixed air.' To that combination of the oxygene with the charcoal, Dr. Beddoes attributes the heat which is manifeftly generated at the beginning of the fermentation.

Art. XI. On the Decompofition of Fixed Air. By Smithfon Tennant, Efq. F. R. S.-The celebrated M. Lavoifier difcovered that fixed air is a compound of charcoal and oxygenous gas; and Mr. Tennant has analysed it into the fame ingredients. He introduces into a glafs tube a little phofphorus, with fome powdered marble, flightly calcined. The tube is coated with fand and clay, to prevent the fudden action of heat; the one end is completely, the other partly, closed, in order that the expanded air may efcape. It is kept fome minutes at a red heat, and then fuffered to cool. Upon breaking it, a black powder is found, confifting of charcoal and a compound of lime and phofphoric acid. In this experiment the oxygene, contained in the carbonic gas of the marble, depofites its charcoal, and unites with the phofphorus; and the acid thus formed combines with the lime by a double affinity.

Art. XII. A Meteorological Journal, principally relating to Atmospheric Electricity; kept at Knightsbridge, from the 9th of May, 1789, to the 8th of May, 1790. By Mr. John Read. Communicated by R. H. A. Bennet, Efq. F.R. S.This journal was kept with affiduous attention, and the instrument for measuring the atmospheric electricity feems to have been well contrived. This electricity was 241 times pofitive, and 156 times negative. Sparks were taken 98 days; and there were only feven days in which no figns of electricity were perceived.

Art..

Art. XIII. Farther Experiments relating to the Decompo fition of dephlogisticated and inflammable Air. By Jofeph Priestley, LL.D. F. R. S.-This is one of the most confused and incoherent of all Dr. Priestley's numerous productions. The main experiment is buried amidst a chaos of digreffions, conjectures, and hypothefes. Nor can we difcover any thing new; for the principal facts were remarked near three years before, by the French academicians. The Doctor procured his oxygenous gas from the yellow product of the folution of nitrous acid, and his hydrogenous gas from iron, by the decompofition of steam. It is evident, that neither of these gafes could have been pure, but must have contained a large admixture of azote. The experiment was made on a very narrow scale, by exploding the two gases in a copper veffel, somewhat larger than a quart bottle.-In all cafes, the whole of the hydrogenous gas is confumed, together with the proportion of the oxygenous neceffary to the inflammation. When therefore the

hydrogenous gas is deficient, it will unite with part of the oxygenous gas to form water; at the fame time, the other part of. the oxygenous gas will combine with the azote contained in the mixture, and yield a fmall portion of nitrous acid. On the other hand, when there is a furplus of hydrogenous gas, the product will be pure water, with a refiduum of hydrogenous and azotic gafes. It is no objection that M. Lavoifier obtained no acid from the flow combuftion of the two gafes; fince the azotic and oxygenous gafes will not combine without the affiftance of intense heat. But the compofition of water has been indifputably established by the late decifive experiment, performed with the utmost care and affiduity, and on a very large fcale, by a deputation of the Royal Academy of Sciences at Paris.

Art. XIV. Experiments on Human Calculi. In a Letter from Timothy Lane, F. R. S. to William Pitcairn, M. D. F. R. S.-Fourteen fpecimens were examined, from which it appears that the human calculi vary much in their properties and constitution, some being foluble in an alkaline lixivium, and others not.

Art. XV. Chermes Lacca. By William Roxburgh, M.D. of Samulcotta. Communicated by Patrick Rufel, M.D. F. R. S.-It is well known that lac is a clufter of the nidi of a certain minute infect. But Dr. Roxburgh here describes the male and female, and remarks fome curious circumstances relating to their economy. The male, in its perfect ftate, is about the fize of a small fly; it has fix legs and four membranaceous wings; its ant nne are clavated and feathered;-it runs and jumps with great activity. The female, in its larva ftate, is red and exceedingly minute; its antenna filiform and

hairy; its tail confifts of two flender white hairs. The larva iffue from their cells about the end of December, and fix themfelves on the hard finall branches of their parent tree, the mimofa. They are foon invefted with a brittle, garnet-coloured crust. About the end of March they have acquired three or four times their original fize, a small cover opens, and they emerge in their perfect ftate. The female fly is rather fmaller than the male, and of a finer red. It has two wings and fix legs; but is not fo active. The females, as in the bees, seem vaftly to out-number the males. The cells are about an eighth of an inch in diameter, and a quarter of an inch deep; they are entirely unconnected. Each contains near an hundred animalcula. A good engraving accompanies this paper.

Art. XVI. The Longitude of Dunkirk and Paris from Greenwich, deduced from the Triangular Measurement in 1787, 1788, fuppofing the Earth to be an Ellipfoid. By Mr. Ifaac Dalby. Communicated by Charles Blagden, M.D. Sec. R. S. This paper contains fome ingenious, though confused, mathematical investigation. On the hypothefis that a meridian on the earth is an ellipfe, Mr. Dalby determines the longitude of Dunkirk to be 2° 22′6′′.8, and that of Paris 2° 20′ 4'9. It deferves to be mentioned, as a proof of the aftonishing accuracy of modern obfervation, that these quantities differ not half a second from those affigned by Dr. Maskelyne in 1787.

Art. XVII. On the Method of determining, from the real Probabilities of Life, the Values of contingent Reverfions in which three Lives are involved in the Survivorship. By Mr. William Morgan, F. R. S.-Mr. Morgan now concludes his intricate and elaborate calculations on this useful branch of political arithmetic; in which he has removed fome difficulties, and detected feveral mistakes, into which his predeceffors had fallen. We hope he will proceed to collect the proper data by which his folutions may be reduced to practice.

Art. XVIII. Abstract of a Regifter of the Barometer, Thermometer, and Rain, at Lyndon in Rutland. By Thomas Barker, Efq. with the Rain in Surrey and Hampshire, for the Year 1790. Communicated by Thomas White, Efq. F. R. S.The greatest heat was 80°, the greatest cold 26°. The quantity of rain which fell at Lyndon in Surrey was 21 inches, that at Selbourn in Hampshire 324. A few remarks are fubjoined, as ufual, on the state of the weather and the circumtances of rural economy.

Art. XIX. Defcription of a fimple Micrometer for meafuring fmall Angles with the Telescope. By Mr. Tiberius Cavallo, F.R. S.-This contrivance is abundantly easy and cheap, and may be of ufe in cafes where no great accuracy is required.

7

Mr.