XXX INTRODUCTION. 



storm, but he believed that nothing violent enough to be called a 

 hurricane could take place, unless a violent rotatory or whirling 

 action be first produced, and that in many, and perhaps most cases, 

 the rotatory portion is not in contact with the earth. 



Mr. Arch Smith said, there was one point which must not be 

 overlooked in any correct comparison of the rival theories. From 

 the principle of the conservation of areas it was perfectly certain, 

 that if a storm was caused in the manner supposed by Mr. Espy, 

 there must be a rotation, greater or less, in the centre. Because, 

 unless the motion of all the currents was accurately directed to 

 one point, or at least their moments in a horizontal plane were 

 equal to zero, which was infinitely improbable, a motion of rota- 

 tion must be the result, as in the instance of the motion of water 

 in a funnel, cited by Mr. Espy. 1 If the central space of compar- 

 ative rest were large, the whirl might be imperceptible ; but if 

 small, as in the case of a water-spout, it must be considerable. 

 Without embracing either theory, he thought it difficult to con- 

 ceive, as he understood Mr. Osier to do, the motion of rotation to 

 be the primary, and the centripetal (which indeed would be cen- 

 trifugal) force to be the secondary phenomenon. But it was com- 

 paratively easy to suppose the centripetal motion to be the pri- 

 mary phenomenon, and quite certain that if so, there must result 

 a secondary phenomenon of rotation, of which indeed some indi- 

 cations appeared in Mr. Espy's maps. 



In making some remarks on the preceding paper, Sir David 

 Brewster observed, that it was impossible to form any decided 

 opinion on the subject, from the great want of well ascer- 

 tained facts ; and as Mr. Espy had founded his theory ex- 

 pressly on observations, often made by himself, it was impos- 

 sible to do justice to his ingenious views until a greater number 

 of facts had been collected. The facts, too, stated by Mr. 

 Espy, were opposed to those observed by others. In the case of 

 hurricanes or tornadoes, the convergency of' the aerial currents in 

 the one theory, and their rotatory motion in the other, were not 

 observed, but inferred from a number of facts ; but as Mr. Espy 

 regarded water-spouts as formed in the same manner as tornadoes, 



1 Mr. Espy's experiments with a funnel, are in opposition to the statement 

 made here. He has performed many, and in all instances where care was taken 

 to have the water still, before removing the finger from the lower end, and 

 letting the water run out, it discharged the whole contents without any whirl- 

 ing motion. The same occurred, whether a funnel was used, or a tub with a 

 hole in the bottom. Mr. Espy acknowledges, however, Mr. Smith's doctrine 

 of the conservation of areas to be correct, and he admits it as highly probable, 

 that spouts sometimes whirl one way, and sometimes another; but generally 

 neither way ; and in all cases, the whirl, if any, would only be perceptible 

 very near the centre. He first supposed that all spouts whirled, and was only 

 compelled to abandon this notion by the facts themselves. 



