b. November 16, 1717 and d. October 29, 1783

French geometer and philosopher. In 1743 he published a “Treatise on Dynamics,” containing an important principle which is known by his name and which initiated a revolution in physico-mathematical sciences. He wrote “Researches on Various Important Points of the System of the Universe” (1754-’56) and “Elements of Philosophy” (1759).

 The world’s a bubble, and the life of man
 Less than a span;
 In his conception wretched, from the womb,
 So to the tomb;
 Curst from the cradle, and brought up to years,
 With cares and fears;
 Who then to frail mortality shall trust,
 But limes the water, or but writes in dust.

 —Bacon

 Let not him that putteth his hand to the plough look backwards;
 Though the ploughshare cut through the flowers of life to its
 fountains.

 —The Courtship of Miles Standish: Longfellow

 Man has plumbed these veiled realms,
 The boundaries of the possible have been extended,
 A mortal, armed with the eye of a giant,
 Has been enabled to see the gleams of light oscillating on the
 Confines of empty space!

 —J. J. Ampere

 1743—D’Alembert published his principle of the equilibrium of forces, called D’Alembert’s principle.

 1829—Gauss enunciated his law of least constraint which may be deduced from D’Alembert’s principle.