VOL. XI.] PHIL0S01>HICAL TRANSACTIONS. 353 



considerable variation in the pressure of the atmosphere by reason of the mineral- 

 steams which are there in the greatest abundance. I am not ignorant that some 

 strongly fermented beds of mineral earths and rusts, which are sometimes barren, 

 send forth a ranker smell than ore itself, which may now and then deceive us j 

 but because for the most part these are concomitants of ore, we may not look 

 upon the attempt as fruitless. 



jin Account of some Books. N° 1 29, p. 742. 



I. Ephemeridum Medico-physicarum Germanicarum Annus IV. et V, Annt 

 1673 et 1674, &c. cum Appendice: Franc, et Lip. 1676, 4to. 



A continuation of the German Ephemerides, noticed in the 1st Vol. of this 

 Abridgement. 



II. Nouvelle Methode en Geometrie pour les Sections des Superficies Co- 

 niques et Cylindriques, qui ont pour Base des Cercles, ou des Paraboles, des 

 Ellipses, et des Hyperboles ; par Ph. delaHire*, Parisien. A. Par. 1673, in 4to. 



This author, in his first proposition, demonstrates all the proportions of the 

 lines, which coming from one point, or being parallel among themselves, and 

 meeting the sections, are cut by these sections, or by the lines that join the 



• Philip de la Hire was bom at Paris, l640, and having learned drawing, perspective and gnomo- 

 nics, to prepare him for his father's profession, that of a painter, he was sent to Italy to improve and 

 perfect himself in that art. But his turn being only to mathematics, he devoted himself entirely ta 

 tliat science, in which he made great progress ; at the same time that he drew well, and was a good 

 landscape painter. On his return to France, he was sent along with M. Picard, into the northern 

 provinces, to take the measvu-ements of the country, in order to prepare a general map of the king- 

 dom, more accurate than had before been drawn, as well as for an extension of tlie meridian before 

 measured and begun by Picard. He became a member of the academy of sciences in l678; and he 

 had the honour of being professor of architectnre and of mathematics to the king. He died in 1718 at 

 78 years of age. The principal of his other numerous and excellent works were, 1. New Elements 

 of Conic Sections, 12mo. 2. A large Treatise on Conic Sections, in folio, l6S5, enlarged from the 

 book above described. 3. Astronomical Tables, 1702, in 4to. 4. School of Land Surveyors, I692, 

 in 12mo. 5. Treatise on Mechanics, 1^95, in 12mo. 6. Treatise on Gnomonics, or Dialling; 

 besides several papers printed in the memoirs of the Academy of Sciences. 



M. de la Hire was a matliematician of the old school, who could never be induced to employ or 

 countenance some of the more modern improvements in analysis, particularly the method of fluxions 

 or differentials. He was nevertheless a sound mathematician, and well skilled in all the other branches 

 of the science, possessing a true taste for the ancient method of geometry, of which his large book 

 on conic sections is a striking instance, at a time when most of his countrymen had abandoned it, 

 In other respects too, it would seem, that la Hire had his peculiarites : it is said that he never passed 

 a windmill without pulling off his hat, in honour of the inventor. 



His son, Gabriel Philip, who survived him only one year, practised physic with reputation, and 

 was also a member of the academy of sciences. He painted for his amusement, as well as studied 

 astronomy and the mathematical sciences; and for several years he undertook the care of calculating 

 ihe ephemerides, called the Connoissance des Temps. 

 VOL. JI, Z Z 



