templated with great pleasure the rugged top of Chiggre, to which we were fast ap. proaching, and where we were to solace ourselves with plenty of good water, Idris, our guide, cried out, with a loud voice, fall upon your faces, for here is the simoom. I saw from the south-east a haze coming, in colour like the purple part of the rainbow, but not so compressed or thick. It did not occupy twenty yards in breadth, and was about twelve feet high from the ground. It was a kind of blush upon the air, and it moved very rapidly; for I scarce could turn to fall upon the ground with my head to the northward, when I felt the heat of its current plainly upon my face. We all lay flat on the ground as if dead, till Idris told us it was blown over. The meteor or purple haze which I saw was indeed passed; but the light air that still blew was of heat to threaten suffocation. For my part, I found distinctly in my breast that I had imbibed a part of it, nor was I free from an asthmatic sensation till I had been some months in Italy, at the baths of Poretta, near two years afterwards." Though the severity of this blast seems to have passed over them almost instantaneously, it continued to blow so as to exhaust them till twenty minutes before five in the afternoon, lasting through all its stages very nearly six hours, and leaving them in a state of the utmost despondency. SIMPLE, something not mixed or compounded, in which sense it stands opposed to compound. SIMPLE, in pharmacy, a general name given to all herbs or plants, as having each its particular virtue, whereby it becomes a simple remedy. SIMPLE Contract, in law, debts by simple contract, are such where the contract upon which the obligation arises is neither ascer tained by matter of record, nor yet by special deed or instrument, but by mere oral evidence, or by notes unsealed; whereas debts by speciality are such whereby the contract is ascertained by deed or instrument, under seal. Simple contract debts are to be paid by executors after debts by speciality. SIMPSON (THOMAS), in biography, professor of mathematics at the Royal Aca. demy at Woolwich, fellow of the Royal Society, and member of the Royal Academy, at Stockholm, was born at Market Bosworth, in Liecestershire, in 1710. His father, a stuff-weaver, taught him only to read English, and brought him up to his own business; but meeting with a scienti fic pedlar, who also practised fortune telling, young Simpson, by his assistance and advice, left off weaving, and professed astrology. As he improved in knowledge, however, he grew disgusted with his pretended art, and, renouncing it, was driven to such difficulties for the subsistence of his family, that he came up to London, where he worked as a weaver, and taught mathematics at his spare hours. As his scholars increased, his abilities became better known, and he published his Treatise on Fluxions, by subscription, in 1737; in 1740 he published his Treatise on the Nature and Laws of Chance; and Essay in Speculative and Mixed Mathematics. After these appeared his Doctrine of Annuities and Reversions; Mathematical Dissertations; Treatise on Algebra; Elements of Geometry; Trigonometry, Plane, and Spherical; Select Exercise; and his Doctrine and Application of Fluxions, which he professes to be rather a new work, than a second edition of his former publication on fluxions. In 1743, he obtained the mathematical professorship at Woolwich Academy; and soon after was chosen a member of the Royal Society, when the president and council, in consideration of his moderate circumstances, were pleased to excuse his admission-fees, and his giving bonds for the settled future payments. At the academy he exerted all his abilities in instructing the pupils, who were the immediate objects of his duty, as well as others whom the superior offi cers of the ordnance permitted to be boarded and lodged in his house. In his manner of teaching he had a peculiar and happy address, a certain dignity and perspicuity, tempered with such a degree of mildness, as engaged the attention, esteem, and friendship, of his scholars. He therefore acquired great applause from his superiors in the discharge of his duty. Mr. Simpson's Miscellaneous Tracts, printed in 4to., 1757, were his last legacy to the public: a most valuable bequest, whether we consider the dignity and importance of the subjects, or his sublime and accurate manner of treating them. The first of these papers is concerned in determining the Precession of the Equinox, and the different Motions of the Earth's Axis, arising from the Attraction of the Sun and Moon. It was drawn up about the year 1752, in consequence of another on the same subject, by M. de Sylvabelle, a French gentleman. Though this gentleman had gone through one part of the sub. Fig.1. Simia satyrus: Orang-outang. Fig.2.5. inus:Barbary ape. Fig.3.S.sphynx: Great baboon. Fig.4.S.leonina: leonine monkey. Fig.5.8. mona: varied monkey. Published Dec 1808 by Longman. Hurst, Rees & Orme. Paternoster Row. ject with success and perspicuity, and his conclusions were perfectly conformable to Dr. Bradley's observations, it nevertheless appeared to Mr. Simpson, that he had greatly failed in a very material part, and that indeed the only very difficult one; that is, in the determination of the momentary alte ration of the position of the Earth's axis, caused by the forces of the Sun and Moon; of which forces, the quantities, but not the effects, are truly investigated. The second paper contains the Investigation of a very exact Method or Rule for finding the Place of a Planet in its Orbit, from a Correction of Bishop Ward's circular Hypothesis, by Means of certain Equations applied to the Motion about the upper Focus of the Ellipse. By this method the result, even in the orbit of Mercury, may be found within a second of the truth, and that without repeating the operation. The third shows the Manner of transferring the Motion of a Comet from a parabolic Orbit, to an elliptic One; being of great use, when the observed places of a (new) comet are found to differ sensibly from those computed on the Hypothesis of a parabolic orbit. The fourth is an Attempt to show, from Mathematical Principles, the Advantage arising from taking the Mean of a Number of Observations, in practical As. tronomy; wherein the odds, that the result in this way is more exact than from one single observation, is evinced, and the utility of the method in practice clearly made appear. The fifth contains the Determination of certain Fluents, and the Resolution of some very useful Equations, in the higher Orders of Fluxions, by means of the measures of angles and ratios, and the right and versed sines of circular arcs. The sixth treats of the Resolution of algebraical Equations, by the Method of Surd-divisors; in which the grounds of that method, as laid down by Sir Isaac Newton, are investigated and explained. The seventh exhibits the Investigation of a general Rule for the Resolution of Isoperimetrical Problems of all Orders, with some examples of the use and application of the said rule. The eighth, or last part, comprehends the Resolution of some general and very important Problems in Mechanics and Physical Astronomy; in which, among other things, the principal parts of the third and ninth sections of the first book of Newton's Principia are demonstrated in a new and concise manner. But what may perhaps best recommend this excellent tract, is the application of the general equations, thus de. VOL. VI. rived, to the determination of the lunar orbit. According to what Mr. Simpson had intimated at the conclusion of his Doctrin of Fluxions, the greatest part of this arduous undertaking was drawn up in the year 1750. About that time M. Clairaut, a very eminent mathematician of the French aca demy, had started an objection against New. ton's general law of gravitation. This was a motive to induce Mr. Simpson (among some others) to endeavour to discover whether the motion of the Moon's apogee, on which that objection had its whole weight and foundation, could not be truly accounted for, without supposing a change in the received law of gravitation, from the inverse ratio of the squares of the distances. The success answered his hopes, and induced him to look further into other parts of the theory of the Moon's motion than he at first intended: but before he had completed his design, M. Clairaut arrived in England, and made Mr. Simpson a visit; from whom he learned, that he had a little before printed a piece on that subject, a copy of which Mr. Simpson afterwards received as a present, and found in it the same things demonstrated, to which he himself had directed his enquiry, besides several others. The facility of the method Mr. Simpson fell upon, and the extensiveness of it, will in some measure appear from this, that it not only determines the motion of the apogee in the same manner, and with the same ease, as the other equations, but utterly excludes all those dangerous kind of terms that had embarrassed the greatest mathematicians, and would, after a great number of revolutions, entirely change the figure of the Moon's orbit. From whence this im. portant consequence is derived, that the Moon's mean motion, and the greatest quantities of the several equations, will remain unchanged, unless disturbed by the intervention of some foreign or accidental cause. These tracts are inscribed to the Earl of Macclesfield, President of the Royal Society. Mr. Simpson's extreme application in this difficult pursuit greatly injured his health. Exercise and a proper regimen were prescribed to him, but to little purpose; for his spirits sunk gradually, till he became incapable of performing his duty, or even of reading the letters of his friends. The effects of this decay of nature were greatly increased by vexation of mind, owing to the haughty and insulting behaviour of his supe M rior, the first professor of mathematics. This person, greatly his inferior in mathematical accomplishments, did what he could to make his situation uneasy, and even to depreciate him in the public opinion; but it was a vain endeavour, and only served to injure himself. At length his physicians advised his native air for his recovery, and he set out in February, 1761 ; but was so fatigued by his journey, that upon his arrival at Bosworth, he betook himself to his chamber, and grew continually worse till the day of his death, which happened on the 14th of May, in the 51st year of his age. SIMSON (DR. ROBERT), in biography, professor of mathematics in the university of Glasgow, was born in the year 1687 of a respectable family, which had held a small estate in the county of Lanark for some generations. He was, we think, the second son of the family. A younger brother was professor of medicine in the university of St. Andrew's, and is known by some works of reputation, particularly "A Dissertation on the Nervous System," occasioned by the dissection of a brain completely ossified. Dr. Simson was educated in the university of Glasgow under the eye of some of his relations who were professors. Eager after knowledge, he made great progress in all his studies; and as his mind did not, at the very first openings of science, strike into that path which afterwards so strongly at tracted him, and in which he proceeded so far almost without a companion, he acquired in every walk of science a stock of information, which, though it had never been much augmented afterwards, would have done credit to a professional man in any of his studies. He became, at a very early period, an adept in the philosophy and theology of the schools, was able to supply the place of a sick relation in the class of oriental languages, was noted for historical knowledge, and one of the most knowing botanists of his time. As a relief to other studies, he turned his attention to mathematics. Perspicuity and elegance he thought were more attainable, and more discernible in pure geometry, than in any other branch of the science. To this therefore he chiefly devoted himself; for the same reason he preferred the ancient method of studying pure geometry. He considered algebraic analysis as little better than a kind of mechanical knack, in which we proceed without ideas, and obtain a result without meaning, and without being conscious of any process of reasoning, and therefore without any conviction of its truth. Such was the ground of the strong bias of Dr. Simson's mind to the analysis of the ancient geometers. It increased as he advanced, and his veneration for the ancient geometry was carried to a degree of idolatry. His chief labours were exerted in efforts to restore the works of the ancient geometers. The inventions of fluxions and logarithms attracted the notice of Dr. Simson, but he has contented himself with demonstrating their truth on the genuine principles of ancient geometry. About the age of twenty-five, Dr. Simson was chosen Regius Professor of Mathematics in the university of Glasgow. He went to London immediately after his appointment, and there formed an acquaintance with the most eminent men of that bright era of British science. Among these he always mentioned Captain Halley (the celebrated Dr. Edmund Halley) with particular respect; saying, that he had the most acute penetration, and the most just taste in that science, of any man he had ever known. And, indeed, Dr. Halley has strongly ex emplified both of these in his divination of the work of "Apollonius de Sectione Spatii," and the eighth book of his "Conics," and in some of the most beautiful theorems of Sir Isaac Newton's "Principia." Dr. Simson also admired the wide and masterly steps which Newton was accustomed to take in his investigations, and his manner of substituting geometrical figures for the quantities which are observed in the phenomena of nature. It was from Dr. Simson that his biographer, to whom we are indebted for this article, learnt, "That the thirty-ninth proposition of the first book of the Principia was the most important proposition that had ever been exhibited to the physico-mathematical philosopher;" and he used always to illustrate to his more advanced scholars the superiority of the geometrical over the algebraic analysis, by comparing the solution given by Newton of the inverse problem of centripetal forces, in the forty-second proposition of that book, with the one given by John Bernoulli in the Memoirs of the Academy of Sciences at Paris for 1713. He had heard him say, that to his own knowledge Newton frequently investigated his propositions in the symbolical way; and that it was owing chiefly to Dr. Halley that they did not finally appear in that dress. But if Dr. Simson was well informed, we think it a |