*THE POPULAR SCIENCE MONTHLY*

Clairaut and Réaumer were leaders in the academy from 1700 to 1750, but Clairaut can not be put by the side of Newton in mathematics, or even of Leibniz, nor, eminent as he was, had he the creative mind of Bernouilli. Yet he was not without honor in other countries as well as in his own. In 1750 his Lunar Tables were crowned by the Academy of St. Petersburg. Réaumer, a many-sided man, carried physics to the heights where Buffon and Cuvier found them. Yet during the first half of the century the academy was unable to point to many men of the first rank among its members. Nearly all of them were men of ability, eager in the pursuit of knowledge, but wanting in those peculiar gifts which belong to men like Newton, or Descartes, or Leibniz. Yet the academy did a vast deal of excellent work. Problems relating to the sun, the moon and the earth were carefully and patiently studied. Newton's theories were shown by D'Alembert to be true, Bradley's discovery of aberration of the stars was made more valuable by measuring that of the planets and of the sun, and by estimating the amount of attraction on the earth. Thury discussed the figure of the earth. Thus, as M. Maury says, "a sort of propylea was formed for the Mécanique celeste of La Place." If Clairaut lacked somewhat in intellectual domination on account of the gruffness of his manners and his love of solitude, in all these respects Réaumer was his opposite. At his reception into the academy he read a paper on gravity, but he devoted his life to the study of the problems of physics. Dissatisfied with the Florence thermometer then in general use, he invented one which met the needs of the time. He made important discoveries in zoology, and wrote a fine history of insects. In practical affairs he was useful in improving the methods employed in the manufacture of pottery, and to his suggestions the iron industry owes a great deal. It is not surprising that with his attractive manners, his genial disposition, he should rule the academy for a score of years, and that he and Clairaut should be universally regarded as its two greatest men, whose fame was eclipsed in later years only by D'Alembert and Buffon.

New sciences like embryology gradually appear, and the sphere of those already studied is largely widened. De Lagny, who died in 1733, made important contributions to geometry and trigonometry, Nicole to the calculus of infinite distances. Joseph Saurin, 24 years older than Nicole, a Cartesian in physics but a Newtonian in mathematics, was also eminent for his knowledge of geometry. Carre published the differential calculus of Marquis de l'Hôpital, and Varignon, Fontaine and Clairaut improved and rendered more valuable the discoveries of Leibniz and Newton. The differential calculus we owe, so it is asserted, to the two Bernouillis, Joseph and Jean. During the period from 1699 to 1750 the academy was an important aid to mechanics, and it made large contributions to the knowledge of astronomy and geometry. In the first quarter of the century Dominique Cassini by his publish