INTRODUCTION. xix 



zinc or tin, from being air tight, will suffer most. 1 The floors 

 from the cellars will also frequently be thrown up, doors and win- 

 dows burst outwards, and bureaus and corks of empty bottles ex- 

 ploded. (181.) All round the tornado at a short distance, pro- 

 bably not more than three or four hundred yards, there will be a 

 dead calm, on account of the annulus formed by the rapid efflux 

 of air above, from the centre of the upmoving and expanding col- 

 umn. In this annulus the air will be depressed, because the ba- 

 rometer stands above the mean there, and all round on the outside 

 of it, at the surface of the earth, there will be a gentle wind out- 

 wards, and of course all the air which feeds the tornado is suppli- 

 ed from within the annulus. Nor is this difficult to understand, 

 when the depression of the air in the annulus is considered, for 

 any amount may be thus supplied by a great depression. Light 

 bodies, such as shingles, branches of trees, sand, pollen of plants 

 in bloom, grain, fishes, 2 frogs, and tadpoles, (82) and drops of rain 

 or water formed in the cloud, will be carried up to a great height, 

 before they are permitted to fall to the earth, provided there is no 

 whirl to throw them out by a centrifugal force ; (32, 33,) for 

 though they may frequently be thrown outwards above, and then 

 descend to a considerable distance at the side, they will meet with 

 an in-blowing current below, which will force them back to the 

 centre of the upmoving current, and so they will be carried aloft 

 again. (32, 82.) 



The drops of rain, however, will frequently be carried high 

 enough to freeze them, especially if they are thrown out above so 

 far as to fall into clear air, for this air will in some cases be thirty 

 or forty degrees colder than the air in the cloud. In this case, if 

 the upmoving column is perpendicular, the hail will be thrown out 

 on both sides, sloping inwards as it falls ; (183 end) and on exam- 

 ination it will be found that two veins of hail fell simultaneously, 

 at no great distance apart. 3 This hail will frequently be found to 



1 Professor Fisher told me that he knew several instances, in Baltimore, of 

 zinc roofs being carried away, while others, in their neighborhood, not air 

 tight, were undisturbed. 



2 While this article is in the press, June 30, 1841, a shower of fishes (one a 

 squid ten inches long) fell in Boston, and the hail stones which fell at the 

 same place had a saline taste. It was nearly calm at the time, but the wind 

 was very violent in the neighborhood. 



3 The annexed chart is copied from the memoirs of the French Academy, 

 vol.90. It represents two veins of hail which fell simultaneously not more 

 than eight minutes at any one place, travelling from the Pyrenees to the Baltic 

 with a velocity of about 50 miles an hour. A A A are veins of rain ; 

 B B are veins of hail. (69.) 



