Page:A biographical dictionary of eminent Scotsmen, vol 6.djvu/339

Rh matics in the university of Edinburgh; a paper written in his Usual flowing, simple, and expressive style. A second was a paper on the causes which affect the accuracy of Barometrical Measurements. A third was Remarks on the Astronomy of the Brahmins. The early eastern astronomy was a subject to which he was very partial, and to which some conceive he has paid more attention than its importance warranted. He fought to a certain extent at disadvantage, from ignorance of the language, and consequently of external evidence as to the authenticity of the remarkable records containing the wisdom of the Brahmins; but he calculated their authenticity from the circumstance, that none but a European acquainted with the refinements of modern science could hare made the calculations on which they might have been forged. The death of his brother James, in 1793, interrupted his philosophical pursuits, by forcing on his management some complicated business, along with the education of his brother's son. In 1795, he published an edition of Euclid's elements for the use of his class. In this work he adopted the plan of using algebraic signs instead of words, to render the proportions more compact and apparent. The plan has been repeatedly practised since that period, and " Playtair's Euclid" is a book well known to the boys in most mathematical schools, by whom, however, it is not always so much admired as it is known. In 1797 he suffered a severe attack of rheumatism, during which he sketched an essay on the accidental discoveries, which have been made by men of science whilst in pursuit of something else, or when they had no determinate object in view; and wrote the observations on the trigonometrical tables of the Brahmins, and the theorems relating to the figure of the earth, which were afterwards published in the Transactions of the Royal Society of Edinburgh. About the same time, his friend Dr Hutton died, and Playfair, who affectionately intended to have written his memoir, found in the study of his works a vast field in which he afterwards distinguished himself, by the preparation of the " Illustrations of the Huttonian Theory of the Earth." Few observers of nature have possessed the power of describing what they have seen, so as to make their facts and deductions perceivable to ordinary thinkers. Playfair possessed the quality, however, to a rare extent; and it was probably its deficiency in the works of his friend Hutton, which prompted him to prepare the elegant and logical "Analysis of the Volcanic Theory of the Earth," which has been so much admired for its own literary merits, and has been the means of rendering popular an important theory which otherwise might have remained in obscurity. It has been said, that the illustration of a theory of the earth was but a profitless employment for so accurately thinking a philosopher, and that the task might have been left to more imaginative minds, whose speculations would have afforded equal pleasure to those who delight in forming fabrics of theory on insufficient foundations. It is true, that even the lucid commentary of Playfair does not establish the Huttonian as a general and undeviating theory, in an undoubted and indisputable situation ; he seems not to have aimed so high ; and from the present state of science, no one can predicate that the elementary formation of the earth, or even of its crust, will ever be shown with chemical exactness. All that can be said is, that in as far as the respective experiments and deductions of the theorists have proceeded, the Huttonian Theory is not directly met by any fact produced on the part of the Neptunians, and the phenomena produced in its favour strongly show indeed show to absolute certainty in some cases the present formation of a great part of the crust of the earth to have been the effect of fire, how operating in respect to the whole substance of the globe it is impossible to determine. The defence of a theory of the earth had for some time been unpopular among many philosophers, from the production of such majestic fabrics of theory as those of Whis-