ELEMENTS OF G E O M E TRY: CONTAINING THE FIRST SIX BOOKS OF EUCLID), WITH A SUPPLEMENT ON THE QUADRATURE OF THE CIRCLE, AND THE GEOMETRY OF SOLIDS: TO WHICH ARE ADDED, ELEMENTS OF PLANE AND SPHERICAL TRIGONOMETRY. BY JOHN PLAYFAIR, F.R.S. Lond. & Edin. PROFESSOR OF NATURAL PHILOSOPHY, FORMERLY OF MATHEMATICS, IN TE UNIVERSITY OF EDINBURGH. FROM THE LAST LONDON EDITION, ENLARGED. D PHILADELPHIA: 1855. HARVARD COLLECE L'B?A?Y Gift of MAR 10 19'38 Entered according to the Act of Congress, in the year One Thousand Eight Hundred and Forty-five, by W. E. Dean, in the Clerk's Office of the Suthern District of New-York. PREFACE. Jr is a remarkable fact in the history of science, that the oldest book of Elementary Geometry is still considered as the best, and that the writings of Euclid, at the distance of two thousand ycars, continue to form the most approved introduction to the mathematical sciences. This remarkable distinction the Greek Geometer owes not only to the elegance and correctness of his demonstrations, but to an arrangement most happily contrived for the purpose of instruction-advantages which, when they reach a certain eminence, secure the works of an author against the injuries of time more effectually than even originality of invention. The Elements of EuCLID, however, in passing through the hands of the ancient editors during the decline of science, had suffered some diminution of their excellence, and much skill and learning have been employed by the modern mathemati cians to deliver them from blemishes which certainly did not enter into their original composition. Of these mathematicians, Dr. Simson, as he may be accounted the last, has also been the most successful, and has left very little room for the ingenuity of future editors to be exercised in, either by amending the text of Euclid, or by improving the translations from it . Such being the merits of Dr. Simson's edition, and the reception it has met with having been every way suitable, the work now offered to the public will perhaps appear unnecessary. And indeed, if the geometer just named had written with a view of accommodating the Elements of Euclid to the present state of the mathematical sciences, it is not likely that any thing new ir. Elementary Geometry would have been soon attempted. But his design was different; it was his object to restore the writings of Euclid to their original perfection, and to give them to Modern Europe as nearly as possible in the state wherein they made their first appearance in Ancient Greece. For this undertaking, nobody could be better qualified than Dr. Simson ; who, to an accurate knowledge of the learned languages, and an indefatigable spirit of research, added a profound skill in the ancient Geometry, and an admiration of it almost enthusiastic. Accordingly, he not only restored the text of Euclid wherever it had been corrupted, but in some cases removed imperfections that probably belonged to the original work : though his extreme partiality for his author never permitted him to suppose that such honour could fall to the share either of himself, or of any other of the moderns. But, after all this was accomplished, something still remained to be done, since, notwithstanding the acknowledged excellence of Euclid's Elements, it could not be doubted that some alterations inight be made that would accommodate them better to a state of the mathematical sciences, so much more improved and extended than at the period when they were written. Accordingly, the object of the edition now offered to the public, is not so much to give the writings of Euclid the form which they originally had, as that which may at present render them most useful. |