THE TORNADO OF 1851. 175 



ping back even to an angle of 180° with the axis. Now, these are just the cases where 

 the reaction pla_ys a very conspicuous part. To illustrate this point, let us suppose a tree 

 to be situated in the axis of the storm, which we will assume to be N. 70° E. As it is 

 struck by the wind, it bends down to the ground, but its southerly roots, being strong, 

 yield under the action without breaking. Reacting under its own elasticity, the tree flies 

 back, and is carried S. 70° W., precisely as if the storm had originally passed over it in 

 that direction. The northerly roots are weak, and break, the tree falls, and its direction 

 is taken as S. 70° W. The yielding or holding of lateral roots may vary this angle more 

 or less, and thus give us any of the exceptional cases which we have observed. This is 

 not a mere theoretical deduction of the mode of action. In many cases, ledges of rock, 

 strong roots, stone walls, &c., did very evidently demonstrate that the tree could not fall 

 in the direction of its surrounding fellows, and its exception to them was amply explained 

 by these causes. In the field notes many remarks are to be found confirming these 

 views, but to transcribe them here, with the necessary references, would swell this 

 memoir beyond proper limits. They are referred to merely by way of inculcating the 

 necessity of caution in reasoning from other exceptional cases, where the fallacy of the 

 reasoning might not be so palpably presented. 



In one sense, most of the observed phenomena may be looked upon as the effects of 

 reaction. The general indication alluded to above, of a dip towards the axis, is most 

 satisfactorily explained, not by considering the trees as thrown down by the direct force 

 of the wind, but rather by regarding the storm as a mass moving with great velocity 

 along its well-defined axis, overthrowing every thing in its way, and leaving behind it a 

 vacuum towards which every thing on the borders of its path collapsed. And confirm- 

 atory of these views are the facts observed with respect to buildings. Roofs were raised, 

 and I was informed that a light muslin cuff was lifted from a bureau, and, as the roof 

 fell back into its place, was caught and held suspended in the crack formed between it 

 and the wall of the room. In one case particularly, of a factory near the West Cam- 

 bridge road, the whole effect produced, and to my own mind well and clearly defined, 

 was precisely what we should have, if we could suddenly place in a vacuum a building 

 filled with atmospheric air of ordinary tension. Even the foundation walls were inclined 

 outwards, and there was every evidence of a force acting from the interior to the 

 exterior. 



The whirl theory, both in its grand convolutions, which may require miles for its 

 exhibition, and in its more limited sphere, in which it drags every tree from its roots, as 

 a screw is drawn from its bed, has its several advocates. With the more extended theory 

 I have nothing to do, leaving that to be studied out from the map. But to those who 



