336 PHILOSOPHICAL TRANSACTIONS. [aNNO 16Q8, 



pounded of the velocity directly, and of the moment of the ordinate inversely, 

 Now let i', {/, z be the fluxions of the absciss, of the ordinate, and of ihe curve 



respectively; then, as above, —- is constant; therefore ^ = 1 ; but we sup- 



y 



posed z {= ^ i'- + y-) to be constant. Therefore that this may be constant 

 unity, and may retain its due dimensions, there will be \ - = — ^ ; and 



after reduction i/ = - . _ -- , which is a known expression of the cycloid pde. 



On the Mineral JVaters at St. ^inund near Tournay. By Mr. Geoffroy.* 



N° 247, p. 430. 



A hiineral water has been found, called St. Amand's water, which has been 

 much used in all sorts of sickness, rather for its novelty, than for its extraor- 

 dinary properties. 



It is situated in a marshy ground ; the basin of the spring is 450 feet square; 

 in the bottom of the basin is mud of 20 feet deep ; below that is sand, which is 

 sometimes very moveable, and at others is very firm. It often casts up a great 

 quantity of sand; and once in a little time more than l6cart loads of it, by 

 which all the basin was bordered. Three sorts of earth are met with ; the 

 uppermost is black, and burns like turf, and with the same smell ; the second 



* Stephen Francis Geoffroy was born at Paris in 1672. His father, who was an apothecary, in- 

 tended him for his own profession ; but young Geoffroy aimed at the dignity of a physician. After 

 attending the lectures of the medical professors at Pari-., he was sent to Montpellier for the com- 

 pletion of his studies. After the peace of Ryswick in I698) although he bad not yet taken his 

 doctor's degree, he accompanied the French ambassador, Marshall Tallard, to England. Here he 

 became acquainted with Sir Hans Sloaiie, and was elected a Fellow of the R. S. in whose trans- 

 actions are inserted several communications of his, chiefly on chemical subject^^. From England 

 he went to Holland, and afterwards to Italy. He did not take his degree of M. D. until 1704. 

 In 1709 he succeeded Ton I nefori, in the professorship of physic at the Royal Coll. at Paris, and in 

 17 1'2 he was appointed chemical professor at the King's Garden. He died in 1731. Besides the 

 papers inserted in the Phil. Trans, and in the Memoirs of the French Academy of Sciences, he wrote 

 a Latin Treatise De Mat. Med. published from his MSS. ten years Lifter his death, under the care of 

 Anthony de Jussieu, in 3 vols. Sv'o. It was afterwards translated into French in 7 vols. 12mo. 1744. 

 The continuation or supplement is by other hands. 



It has been remarked by a celebrated physician, that although GeoiTroy's Mat. Med. is a work of 

 some value both in regard to the extent and variety of matter ; yet that in his accounts of the virtues 

 of plants, he has yielded too readily to the authority of preceding writers, and in numerous instances 

 has admitted, without the least judgment or selection, their extravagant commendations ; and some- 

 times their mistakes. He was moreover too fond of explaining the medicinal powers of vegetables 

 by the quantity of salts, oil, earth, &c. obtained from them by chemical analysis; a most fallaciou* 

 mode (as the physician before quoted has remarked) of determining their action. 



