Explanation of the EffeB of the Water blowing Machine. 489 



plained the produdlon of wind by a fall of water *. Barthes, tKe father, has given a 

 theory which appears to me to be defe£tive in many refpccSls f . Dietrich was of opinion, 

 that this wind is produced by the decompofition of water J. Fabri had a fimilar notion in 

 the lad century §. Moft philofophers are well acquainted with this kind of engine H. 



I fliall begin with an idea, tlie foundation of which did not efcape t^he penetration of 

 Leonardo Da Vinci. Suppofe a number of equal balls to move in contact with each other 

 along the horizontal line A B, fig. 16. Plate XXII. Imagine them to pafs with an uni- 

 form motion, at the rate of four balls in a fecond. Let us take B F, equal to 1 6 feet 

 Englifli. During each fecond four balls will fall from B to F, and their refpe£l:ive diftances 

 in falling will be nearly BC=i,CD = 3, DE = 5, EF = 7. We have here a very 

 evident reprefentation of the feparation, and fucceffive elongation, which tlie accelerating 

 force of gravity produces between bodies which fall after each other. 



The rain water flows out of gutters by a continued current 5 but during its fall it fepa- 

 rates into portions in the vertical direction, and ftrikes the pavement with di(lin£t blows. 

 The water likewife divides, and is fcattered in the horizontal direftion. The ftream 

 which iffues out of the gutter may be one inch in diameter, and ftrike the pave- 

 ment over the fpace of one foot. The air which exifts between the vertical and hori- 

 zontal feparations of the water which falls, is impelled and carried downwards. Other air 

 fucceeds laterally ; and in this manner a current of air, or wind, is produced round the place 

 ftruck by the water. I went to the foot of the cafcadcs which fall from the Glaciere of 

 La Roche Melon, on the naked rock at La Novalefe, towards Mount Cenis, and found the 

 force of the wind to be fuch as could fcarcely be withflood. If the cafcade falls into a 

 bafon the air is carried to the bottom, whence it rlfes with violence, and difperfes the water 

 all round in the form of a mift. 



The water which is precipitated in the hollow internal parts of mountains carries the air 

 with it, which afterwards iffuing forth from apertures at the foot of the mountain, pro- 

 duces thofe natural blafts, thofe ventaroli % which are moft frequently obferved in the vol- 

 canic mountains, bccaufe thefe mountains are moft commonly hollow within. 



Let B C D E, fig. 16. reprefent a pipe, through which the water of a canal A B falls into 

 the lower receiver, M N. The fides of the tube have openings all round, through which 

 the air freely enters to fupply what the water carries down in its fall. This mixture of wa- 

 ter and air proceeds to ftrike a mafs of ftone Q^ whence rebounding through the whole 

 width of the receiver M N, the water feparates from the air, and falls to the bottom at X Z, 

 whence it is difcharged into the lower channel or drain, by one or more openings, T, V. The 



* Mundus Subterr. lib. XIV. Cop.'j, edit. i66z. 



"l- Memoires des Savans etrangers, vo). III. p. 378. 



% Git-s de Mineral des Pvrenees, p. 48, 49. 



§ Phyfic. traft I. lib. II. prop. 243. 



I Aw des Forges, part II. Mariotte des Eaux, part I. difc. III. Tranfaft. No. 473, &c. 



^ Thefe veniaroli arc fometimes produced by the difference of temperature between the air of the cavern 



• and the external air. V. Frors the effifls they fecm to be oftener proiluced by this lad caufc, than by a 



fall of water. On this fuhjedl in general, ,n..meiy, the cold winds which iffue out of the earth, fee 



Philof. Journal, I. 219. — J^. 



air 



