On the whirling Eddies of defcending IVater. 15- * 



If the aflumed pofitlons in this theory do not abfolutely coincide w ith nature, they approach 

 its efFedls very nearly. It is not only poflible, but there does exift m nature, a whirling ftream, 

 of which the cavity turns its convex part to the axis, and in which /=:V' very nearly, as is 

 fhewn by experiment. 



Experiment xxvi. Let the orifice E F be opened, and any motion whatever be imprefFjd on 

 the fluid, independent of that which its gravity, and the preffure of the circumambient particles, 

 tend to produce ; the turning immediately begins, and is feen to be more rapid in thofe parts of 

 the fluid which are neareft the bottom. The caufe of this is, that the motion D B is more 

 convergent and perceptible in thofe parts which are neareft the orifice E F*. The centri- 

 petal force D C, produces its efft£t there rather than at the upper parts. Thefe laft afterwards 

 fall into the cavity which begins to be formed below, by which means chcy alfo acquire a cen- 

 tripetal force, and the funnel or cavity opens to a much greater height, than that in which the 

 convergence of fluid filaments is obferved towards the orifice E F, in water which is lefs 

 agitated. 



Experiment xxvii. Place a floating body at the furface of the fluid, of fufKcient magnitude 

 to prevent the formation of the cavity. If the fluid be much agitated, the cavity will take 

 place at the lower part, and air will introduce itfelf through the opening E F. Whence it 

 follows, that the prefTure of the atmofphere on the upper furface of the fluid is not the caufe of 

 the cavity, which afl"umes the Ihape of a funnel. The air does not enter but becaufe it 

 finds an empty fpace formed by a centrifugal force. 



Experiment xxviii. When the fluid remains in a ftate of tranquillity without eddies, the veflel 

 empties itfelf in forty feconds ; but when the circular motion takes place, the evacuation is ac- " 

 complifhed in fifty feconds, more or lefs. It cannot, therefore, be faid in general terms, that 

 the whirling flream aljforbs and draws down bodies through the opening E F with more force 

 than if no fuch circulation took place. 



Experiment xxix. Pour aftratum of oil upon the water of the vefTel. As foon as the funnel 

 forms itfelf, the oil ruflies down, and iflues out before the greateft part of the lower water, 

 upon which it refted. The portions of oil partake lefs of the rotation of the lower water ; 

 having lefs denfity, they likewife recede lefs from the axis than the water ; in confequence of 

 which, as they occupy the interior part of the funnel, and are unfupported, they flow out 

 firft. 



Experiment xxx. Every other fmall body which floats on the water in the vefTel, a£ls ire 

 the fame manner as the oil, provided its dimenfions be very fmall. If the volume of the body 

 be fomewhat greater, while it approaches the cavity, to fall therein, its extremity, which, is 

 neareft the axis, comes into a place where the circulation is more rapid. This rapidity of 

 motion impreflTed at one extremity of the floating body, is tranfported by the laws of mechanics, 

 to its centre of gravity, which is more remote from the axis, in a fituation where the circular 

 motion is flower, confequently the body recedes from the edge of the cavity into which it was 

 about to fall. It returns a ftiort time afterwards, is again repelled, and thefe alternate motions 

 continue as long as the circumftances which produced them. Laflly, if the body which floats 



* Bernouilli. Hydrod. feft. 4, §. 3. BolTut, art, 427. 



■ . at 



