1820.] Scientific Intelligemem 305 



the lower end being plunged into water, the water will rise by 

 the effect of the rotation. The author also calculates the effect 

 of a machine formed of two paraboloids, turning together on the 

 same vertical axis, and united together by inclined partitions. 



Archimedes's screws form that kind in which the axis is 

 inchned. Daniel BournouUi devoted some attention to their 

 theory, but he did not exhaust the subject, as M. Navier has 

 done. In respect to the case in which a pipe of an uniforni 

 diameter, bent spirally on a cylinder whose axis is inclined, is 

 filled alternately with water and with air, he demonstrates in a 

 simple and elegant manner that the surface of the water must be 

 a paraboloid, having the axis of the cylinder for one of its diame- 

 ters, and the surface of the water at rest for a tangent plane at 

 the extremity of the diameter. 



For the common screw, formed by the revolutions of an mter- 

 nal screw, in a circular cylinder, after having sought the quanti- 

 ties of water contained in, each turn of the screw, he draws up 

 tables to shorten the necessary calculations, accordmg as the 

 turns of the screw are more or less near, and their axis more oc 

 less inclined. 



The very extensive work of which we have just given an 

 account, say the Committee, appears to us to be of the number 

 of those which the Academy ought, by its approbation, more 

 especially to encourage. To extend by an uniform progress the 

 theoretical methods of appreciating the effects of machnies is to 

 narrow gradually the circle of empiricism : it is to furnish artists 

 with general means of becoming acquainted with the advantages, 

 and dTsadvantages they may hope or fear from their inventions. 



The Academy has, in consequence, ordered, that the treatise 

 of M. Navier should be printed in the next volume of the Savans- 

 Etrangers. 



(To he continutd.) 



Article X. 



SCIENTIFIC INTELLIGENCE, AND NOTICES OF SUBJECTS 

 CONNECTED WITH SCIENCE. 



I. Boiling Springs in the Island of St. Lucie. 



The face of the country is extremely rugged, and inter- 

 sected in all directions by high pointed hiUs. In one place there 

 still is a curious phenomenon. At the head of an extensive, 

 valley, there are situated a number of boiling springs, the nura- 

 ber of which varies at different times, but generally eight or t.en 

 of them discharge water at the same lime. This, hovvevec, is 

 quite uncertain, as they frequently dry up, and again burst 

 forth, and flow with much violence. The ebullition of some oC 



Vol. XV. N° IV. TJ 



