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Hunter, Esq. F.R.S. It is curious to observe how Nature

sports in her productions. In her wild excursions she is per..haps more astonishing than in her uniform plans. In these un

guarded moments, the sometimes lays aside part of that mystery with which fhe is commonly enveloped; and hence the detection of her deviations often throws light upon her ordinary course. The subject of this paper is a moniter of a fingular kind. The lusus was wholly internal, and escaped common observation. The person was a male near forty years of age, fomewhat above the middle size, and of a clean active shape. Upon dissection the parts were found reversed. 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 similar.' transposition took place in the abdomen. "The blood vessels were very irregular in their positions and ramifications. The structure of the brain and of the organs of sense, offered nothing remarkable.

Art. XXII. On the Georgian Planet and its Satellites. By William Herschell, LL.D.F.R.S. We may state the general result of Dr. Herschell's abfervations with regard to the satellites of the new planet. The diameter is 34,217 miles, and, seen from the earth, it subtends an angle of 4". The bulk of the planet is eighty times that of the earth, and its density about s.

The first satellite performs its revolution in 8 days 17 hours · I' 19'', and its distance is 33''; the second 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 In-
flammable Airs. By William Austin, M. D. Fellow of the
College of Physicians. Communicated by Charles Blagden, M.D.
Sec. Ř. S. The resolution of volatile alkali into the hydrogenous
and azotic gas had occurred to several chemists, but it was first
completely demonstrated by the ingenious M. Berthollet. Se-
veral attempts have been made to recompose the alkali from
these elastic fluids, but without success. When hydrogen and
azote assume the elastic form, they absorb a large portion of
caloric, which increases with their rarity; and they cannot be
brought to combine, unless a fubstance be presented which has a
stronger attraction for the matter of heat. Dr. Austin tried to
deprive them of their latent heat, and to form an union by the
application of cold and the addition of other gases; but did not
succeed. Hence these gases cannot be converted into volatile
alkali, except at the instance of their extrication. If powdered
tin be moistened with nitrous acid and fixed alkali, or quick-lime

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be added, the smell of volatile alkali is immediately perceived. In this case the oxygen from the water and the acid unite to the metal; while the hydrogen and azote form volatile alkali. The fixed alkali seems only to assist the decomposition. Dr. Austin fucceeded in a very beautiful experiment. He introduced azotic gas into a cylindrical glass tube inverted in quicksilver, and afterwards iron-filings, moistened with distilled water. The hydrogen detached from the water by the contact of the iron, united with the azotic gas, and formed volatile alkali. The experiment succeeds with atmospheric air, though it requires á longer time to be manifest. Hence when it rusts in contact with water, it forms volatile alkali. The component gases are constantly 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 Divisors of Numbers. By Edward Waring, M.D. F.R. S. This paper contains some curious analytical disquisitions. It is to be considered as an addition to a treatise published several years ago by the author, entitled Meditationes Algebraicæ. 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, Esq. F.R.S. and A. S. When a body is converted from a solid to a fluid state, a quantity of its heat disappears, or becomes latent. This beautiful discovery 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 salt in water. The people of India employ saltpetre to cool their liquors. This is, in some degree, the effect of every saline solution; but the intensity of the cold depends upon the capacity of the falt for heat, and its degree of solubility. After water is completely saturated with one species of falt, it can still dissolve considerable portions of other kinds. Hence in this way a greater quantity of solid matter may be converted into fluid, and consequently a more intense degree of cold produced. The mixtures which Mr. Walker has discovered are most powerfully frigorific. Crystallised nitrated ammonia, reduced to very fine powder, sunk the thermometer, during its solution in rain water, 49o. Equal parts of sal ammoniac and nitre in powder, make a cheap and convenient compofition for producing cold. It sinks the thermometer 36o. Equal parts of nitrated ammonia and mineral alkali produce a cold even 2 3

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of 57o. But one of the most 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; 37 ni

trated ammoniac. This depresses the thermometer 52o._Upon , the whole, these experiments are not only curious, but may

prove beneficial to mankind. By those frigorific mixtures we may always produce ice in our climate, and even in the tropical regions; as the mean annual temperature seldom exceeds 80° we may generally be able to bring on congelation. The method proposed by the evaporation of æther is more expensive, and, requiring the assistance of the air-pump, it is very inconvenient.

Art. XXVI. A Description of an Instrument 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 instrument; but it would be difficult to convey a distinct idea, of it without the assistance of a figure. It is constructed upon the principle discovered by Volta, that the capacity of bodies for the electrical fluid is increased by their apposition. It bears a con, siderable resemblance to Bennet's doubler, and confirms the remark of Cavallo, that the electrical equilibrium which subfifts among connected bodies is not quite perfect.

Art. XXVII. Abstract of a Register of the Barometer, Thermometer, and Rain, at Lyndon in Rutland; with the Rain in Hampshire and Surrey, in 1787. Also some Account of the annual Growth of Trees.' By Thomas Barker, Esq. Com municated by Thomas White, Esq. 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 observe the great difference in the quantity of rain fallen near the same 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 ash is nearly the fame, about an inch in girth annually. Hence large trees acquire greater additions to their bulk in the same time than small ones.

Art. XXVIII. On the Era of the Mahometans, called the Hejerà. By William Marsden, Esq. F. R. S. and A.S. The flight of Mahomet from Mecca to Medina was, eighteen years, afterwards, distinguished as the crisis of the new religion, and established as an epoch to which the transactions of the faithful should in future be referred. It commenced at sunset, from which the Arabs begin their day, on Thursday the 15th July, A. D. 622. The Mahometan year consists of twelve lunar., months, without any intercalation; and therefore it anticipates,

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the completion of the solar 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 second day after the conjunction. This is announced by: persons placed on the pinnacles of the mofques, and other ele. Vated places, to the people below, who welcome it with the . found of instruments, firing of guns, and other demonstrations of respect and zeal. The political mode of reckoning was regulated by a cycle of thirty years. The mean synodic revolu. tion, according to the Arabs, was 29 days and 127103 hours; and consequently the lunar year consisted of 354 days 8,804 hours. We cannot omit to observe the astonishing accuracy of the astronomical observations made in the East; the country whence we derived our arts, our science, and our religion. - The length of the Arabian lunat month differs only three seconds from the most accurate modern observations. The fraction is of a day is exactly 8 hours and 48 ininutes, or 87904 hours, the excess of the lunar year above 354 days. Hence the cycle consisted 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 superior to the clumsy intercalations employed in Europe ! The Mahometan months consist alternately of 29 and 30 days; but in the years of excess an intercalary day is besides 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 present year of the Hejera, 1204, began on Monday, 21st September, 1789; the next, 1205, commences on Friday, joth 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, Esq. F.R.S. 4to. 51. 5s.." · boards. Edinburgh, printed : Ĝ. G. J. and J. Robinson,

London. 1790. AT last, after the lapse of full fixteen years, when the long

delay had nearly changed hope into despair, the desire of the learned and inquisitive of every nation is gratified; and the general burst of impatient curiosity will welcome thefe volumes by exclamations like thofe with which Æneas receives the ghost of Hector:

24.

Quæ tantæ tenuêre moræ ? quibus--ab oris,

Expectate, venis ? We, for our parts, make haste to gratify our readers with a full and distinct account of a work expected so long, and so ardently desired; for in these days of rapid communication and widely diffused information, we may fairly presume 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 also whom the vague desire of feeing curious things, or the tenor of their particular studies has led to the British botanic gardens, it must have happened to see some specimens of those vegetable treasures which the adventurous traveller gathered on his long and perilous expedition. Among these, that which saved the life, and bears the name of its discoverer, the Brucea Antidysenterica, is, if we mistake not, the most common. From the new plants, therefore, received as such by the universal consent of botanists, there arises 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 dissatified and uncomfortable till his notions are in some measure settled as to the degree of credit to which the narrative is entitled, we begin by opposing the abovementioned strong presumption 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 strong protestations of veracity, dispersed through the different volumes, allude ; and we suppose of course the author to be no ftranger to it, though it is no where formally refuted, or even distinctly noticed, And why should one, who has never been regularly accused, enter upon a superfluous defence? There is,

besides, no want of other external evidence, such as must imme- diately difpel whatever mist of doubt, the circulation of an anec

dare improbable and scandalous, might spread over Mr. Bruce's pages. In truth, the anecdote, as we have often heard it re: lated, is, if properly considered, foreign to the question concerning the authenticity of the travels; if true in the most unfavourable statement, it would only shew, what is so commonly seen, how a man in conversation with a personage placed in a very elevated station niay be disconcerted, or a sudden swell of vanity hurry him into an imprudent assertion, and render him nas so much criminal as ridiculous,

In the examination of this work many readers will go along with us with minds more at ease if we produce, of that other external evidence, so much as leads us irresistably to believe

that

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