Hunter, Efq. F. R. S. It is curious to obferve how Nature fports in her productions. In her wild excurfions fhe is perhaps more aftonishing than in her uniform plans. In these unguarded moments, the fometimes lays afide part of that mystery with which fhe is commonly enveloped; and hence the detection of her deviations often throws light upon her ordinary courfe. The fubject of this paper is a moniter of a fingular kind. The lufus was wholly internal, and escaped common obfervation. The perfon was a male near forty years of age, fomewhat above the middle fize, and of a clean active fhape. Upon diffection the parts were found reverfed. The right auricles and ventricles of the heart occupied the place of the left. The right lung was divided into two lobes, and the left into three; exactly contrary to what is found in ordinary cafes. A fimilar tranfpofition took place in the abdomen. The blood veffels were very irregular in their pofitions and ramifications. The ftructure of the brain and of the organs of fenfe, offered nothing remarkable. Art. XXII. On the Georgian Planet and its Satellites. By William Herfchell, LL. D. F. R.S. We may state the general refult of Dr. Herfchell's obfervations with regard to the fatellites of the new planet. The diameter is 34,217 miles, and, feen from the earth, it fubtends an angle of 4". The bulk of the planet is eighty times that of the earth, and its density about. The firft fatellite performs its revolution in 8 days 17 hours 1'19", and its diftance is 33"; the fecond revolves in 13 days 11 hours and 5 minutes, and at the distance of 44". Its axis is above 80° inclined to the ecliptic. Art. XXIII. Experiments on the Formation of Volatile Alkali, and on the Affinities of the Phlogisticated and light Inflammable Airs. By William Auftin, M. D. Fellow of the College of Physicians. Communicated by Charles Blagden, M. D. Sec. R. S. The refolution of volatile alkali into the hydrogenous and azotic gas had occurred to several chemists, but it was first completely demonftrated by the ingenious M. Berthollet. Several attempts have been made to recompofe the alkali from thefe elaftic fluids, but without fuccefs. When hydrogen and azote affume the elaftic form, they abforb a large portion of caloric, which increases with their rarity; and they cannot be brought to combine, unless a fubftance be prefented which has a ftronger attraction for the matter of heat. Dr. Auftin tried to deprive them of their latent heat, and to form an union by the application of cold and the addition of other gafes; but did not fucceed. Hence these gafes cannot be converted into volatile alkali, except at the inftance of their extrication. If powdered tin be moiftened with nitrous acid and fixed alkali, or quick-lime be be added, the smell of volatile alkali is immediately perceived. In this cafe the oxygen from the water and the acid unite to the metal, while the hydrogen and azote form volatile alkali. The fixed alkali feems only to affift the decompofition. Dr. Auftin fucceeded in a very beautiful experiment. He introduced azotic gas into a cylindrical glafs tube inverted in quickfilver, and afterwards iron-filings, moistened with diftilled water. The hydrogen detached from the water by the contact of the iron, united with the azotic gas, and formed volatile alkali. The experiment fucceeds with atmospheric air, though it requires á longer time to be manifeft. Hence when it rufts in contact with water, it forms volatile alkali. The component gafes are conftantly produced in all parts of the earth; and hence the origin of volatile alkali in coal mines and in volcanos. It appears the quantity of azotic gas in alkaline air is about four times that of the hydrogen. Art. XXIV. Some Properties of the Sum of the Divifors of Numbers. By Edward Waring, M. D. F. R. S. This paper contains fome curious analytical difquifitions. It is to be confidered as an addition to a treatise published several years ago by the author, entitled Meditationes Algebraica. From its nature it does not admit of abridgment. Art. XXV. Experiments on the Production of artificial Cold. By Mr. Richard Walker, Apothecary to the Radcliffe Infirmary at Oxford. In a Letter to Henry Cavendish, Efq. F. R. S. and A. S. When a body is converted from a solid to a fluid ftate, a quantity of its heat disappears, or becomes latent. This beautiful difcovery of the great Dr. Black is undoubtedly one of the most important in the science of chemistry. It has extended our views of the nature of heat, and thrown light upon many natural phenomena. Hence cold is produced during the folution of any falt in water. The people of India employ faltpetre to cool their liquors. This is, in fome degree, the effect of every faline folution; but the intenfity of the cold depends upon the capacity of the falt for heat, and its degree of folubility. After water is completely faturated with one fpecies of falt, it can ftill diffolve confiderable portions of other kinds. Hence in this way a greater quantity of folid matter may be converted into fluid, and confequently a more intenfe degree of cold produced. The mixtures which Mr. Walker has difcovered are moft powerfully frigorific. Cryftallifed nitrated ammonia, reduced to very fine powder, funk the thermometer, during its folution in rain water, 49°. Equal parts of sal ammoniac and nitre in powder, make a cheap and convenient compofition for producing cold. It finks the thermometer 36°. Equal parts of nitrated ammonia and mineral alkali produce a cold even of 57°. But one of the moft powerful mixtures is two parts fuming nitrous acid and one part water, well mixed, and reduced to the temperature of the atmosphere, 4 Glauber's falt, 3 nitrated ammoniac. This depreffes the thermometer 52°.-Upon the whole, thefe experiments are not only curious, but may prove beneficial to mankind. By thofe frigorific mixtures we may always produce ice in our climate, and even in the tropical regions; as the mean annual temperature feldom exceeds 80° we may generally be able to bring on congelation. The method propofed by the evaporation of æther is more expensive, and, requiring the affiftance of the air-pump, it is very inconvenient. Art. XXVI. A Defcription of an Inftrument which, by the turning of a Winch, produces the Two States of Electricity without Friction or Communication with the Earth. In a Letter from Mr. William Nicholson to Sir Joseph Banks, Bart, P. R. S. This appears to be an ingenious and elegant inftrument; but it would be difficult to convey a diftinct idea of it without the affiftance of a figure. It is conftructed upon the principle difcovered by Volta, that the capacity of bodies for the electrical fluid is increased by their appofition. It bears a confiderable resemblance to Bennet's doubler, and confirms the remark of Cavallo, that the electrical equilibrium which fubfifts among connected bodies is not quite perfect. Art. XXVII. Abstract of a Regifter of the Barometer, Thermometer, and Rain, at Lyndon in Rutland; with the Rain in Hampshire and Surrey, in 1787. Alfo fome Account of the annual Growth of Trees. By Thomas Barker, Efq. Communicated by Thomas White, Efq. F. R. S. The greatest height of the mercury in the barometer was 30,13 inches, the lowest 28,15, and the medium 29,415. The medium temperature of the year 50°. It is curious to obferve the great difference in the quantity of rain fallen near the fame place. In the fmall county of Rutland the fall at one place was 36 inches, in another only 22.-The growth of the oak and afh is nearly the fame, about an inch in girth annually. Hence large trees acquire greater additions to their bulk in the fame time than fmall ones. Art. XXVIII. On the Era of the Mahometans, called the Hejera. By William Marsden, Efq. F. R. S. and Á. S. The flight of Mahomet from Mecca to Medina was, eighteen years afterwards, diftinguished as the crisis of the new religion, and eftablished as an epoch to which the transactions of the faithful fhould in future be referred. It commenced at funfet, from which the Arabs begin their day, on Thursday the 15th July, A. D. 622. The Mahometan year confifts of twelve lunar. months, without any intercalation; and therefore it anticipates the 864 the completion of the folar year, and revolves through all the seasons. There are, however, two modes of reckoning; the vulgar, and political. In the former the year commences from the first appearance of the new moon, on the evening of the first or fecond day after the conjunction. This is announced by perfons placed on the pinnacles of the mofques, and other ele vated places, to the people below, who welcome it with the found of inftruments, firing of guns, and other demonstrations of refpect and zeal. The political mode of reckoning was regulated by a cycle of thirty years. The mean fynodic revolu tion, according to the Arabs, was 29 days and 12 hours; and confequently the lunar year confifted of 354 days 8, hours. We cannot omit to observe the astonishing accuracy of the aftronomical obfervations made in the Eaft; the country whence we derived our arts, our science, and our religion. The length of the Arabian lunat month differs only three feconds from the most accurate modern obfervations. The fraction of a day is exactly 8 hours and 48 minutes, or 8,86 hours, the excess of the lunar year above 354 days. Hence the cycle confifted of 11 years of 355 days, and 19 of 354. The whole error amounted, in a period of thirty years, only to 18 minutes. How much fuperior to the clumfy intercalations employed in Europe! The Mahometan months confift alternately of 29 and 30 days; but in the years of excess an intercalary day is befides added to the last month. The annual anticipation of Mahometan years, 10 days and 21 hours, or nearly 11 days. Hence their periods may be calculated. The prefent year of the Hejera, 1204, began. on Monday, 21ft September, 1789; the next, 1205, commences on Friday, 10th September, 1790, &c. This elegant and ingenious paper clofes with a table exhibiting the correspondent years of the Hejera with those of the Christian era. ART. VII. Travels to discover the Source of the Nile, in the Years 1768, 1769, 1770, 1771, 1772, and 1773. In Five Volumes. By James Bruce, of Kinnaird, Efq. F. R. S. 4to. 51. 5s. boards. Edinburgh, printed: G. G. J. and J. Robinfon, London. 1790. AT laft, after the lapfe of full fixteen years, when the long delay had nearly changed hope into defpair, the defire of the learned and inquifitive of every nation is gratified; and the general burft of impatient curiofity will welcome these volumes by exclamations like thofe with which Æneas receives the ghoft of Hector: Quæ tanta tenuêre mora? quibus--ab oris, We, for our parts, make hafte to gratify our readers with a full and diftinct account of a work expected fo long, and so ardently defired; for in these days of rapid communication and widely diffused information, we may fairly prefume that there is no individual, in any degree attentive to literature and science, to whom the name of ABYSSINIAN BRUCE is either unknown or indifferent. To most of those alfo whom the vague desire of feeing curious things, or the tenor of their particular ftudies has led to the British botanic gardens, it must have happened to see fome fpecimens of thofe vegetable treasures which the adventurous traveller gathered on his long and perilous expedition. Among thefe, that which faved the life, and bears the name of its difcoverer, the Brucea Antidysenterica, is, if we mistake not, the most common. From the new plants, therefore, received as fuch by the universal consent of botanists, there arifes a sufficient proof that the importer must have visited regions unknown and unexplored. As in fitting down to a book of this nature every reader feels diffatified and uncomfortable till his notions are in fome meafure settled as to the degree of credit to which the narrative is entitled, we begin by oppofing the abovementioned strong prefumption to the tale of calumny, that has put on an hundred forms, and been whispered into the ears of tens of thousands. To this tale we conjecture, and not merely to Baron Tott, that numerous and ftrong proteftations of veracity, difpersed through the different volumes, allude; and we fuppofe of course the author to be no ftranger to it, though it is no where formally refuted, or even diftinctly noticed, And why fhould one, who has never been regularly accufed, enter upon a fuperfluous defence? There is, befides, no want of other external evidence, fuch as muft immediately difpel whatever mift of doubt, the circulation of an anecdate improbable and fcandalous, might fpread over Mr. Bruce's pages. In truth, the anecdote, as we have often heard it related, is, if properly confidered, foreign to the queftion concerning the authenticity of the travels; if true in the most unfavourable statement, it would only fhew, what is so commonly feen, how a man in converfation with a perfonage placed in a very elevated ftation may be disconcerted, or a fudden swell of vanity hurry him into an imprudent affertion, and render him not fo much criminal as ridiculous, In the examination of this work many readers will go along with us with minds more at eafe if we produce, of that other external evidence, fo much as leads us irrefiftably to believe that |