Chap, n.] Whirlwinds. 47 \ 



different form. It is therefore not difficult to con- 

 ceive, that when any part of the column of air upon 

 the furface of the earth or water is fuddenly rarefied, 

 either by electricity or any other caufe, a vacuum, at 

 lead comparatively to the reft of the air, will imme- 

 diately take place, and the circumambient air rufhing 

 in at once from every quarter to fill the void, a con- 

 flict of winds enfues, and confequently a circular mo- 

 tion, by which light bodies will be taken up and turned 

 round with confiderable velocity; this 1 violent rufhing 

 of the air on all fides into the vacuum then forms 

 what is commonly called at land a whirlwind. 



When this vacuum takes place at fea, from the 

 nature of fluids, the water will rife to a certain height 

 by the prefiure of the atmofphere, as in a common 

 pump ; but as the vacuum is not quite perfect, the 

 water will be divided into drops, and as thefe va- 

 cuums are generally caufed by heat, it will be rarefied 

 when it reaches the upper regions of the atmolphere, 

 and affume the appearance of a cloud. 



Mr. Oliver *, whofe theory I have adopted with 

 little variation, illuftrates the phenomenon by a very 

 eafy experiment. In a ftiff paper card he made a 

 hole juft large enough to infert a goofe quill ; after 

 cutting the quill off fquare at both ends, he laid the 

 card upon the mouth of a wine glafs, filled with water 

 to within a fifth or fixth part of an inch from the 

 lower orifice of the quill ; then applying his mouth to 

 the upper part, he drew the air out of the quill, and 

 in one draught of his breath drew in about a fpoon- 

 ful of water; and this he was able to repeat, the quill 

 remaining as before. The water, he adds, did not 

 afcend to his mouth in a dream, as it would have done 



*' Philad. Tranf. vol. ii. 



H h 4 bad 



