•with reference to the Whirlwind Theory of Storms. 363 



If a whirlwind figure having a diameter of three or four 

 hundred yards by the scale of Professor Bache's figure, 

 (plate iii. fig. 3*) be drawn on tracing paper, with involute 

 whirling lines representing, horizontally, the course of the 

 wind from the exterior to the interior of the tornado, and if 

 the centre or axis of this figure be passed from west to east 

 along the line pursued by the axis of the tornado as indicated 

 on the plate, revolving at the same time to the left with a ve- 

 locity greatly exceeding its advancing motion, it may be seen 

 that the wind of the whirl will be indicated as beginning at 

 this building from nearly south, i. e. moving " to the west of 

 north," nearly, or in the general direction of the first furrows 

 in the ground. It will also be seen, that the wind of the whirl, 

 changing by south-west, and having its gyrations quickened 

 near the centre, would, immediately after the passing of its 

 axis, exhibit its greatest force from the western quarter, cor- 

 responding to the second movement of the posts in the ground ; 

 the wind veering from thence towards the north-west as the 

 tornado passed away: thus showing two directions of wind 

 which sufficiently coincide with the two movements of the 

 posts of the building " to the west of north," and subsequently 

 "to the eastward," or "nearly at right angles" to its first course, 

 according to the descriptions and plan of Professor Bache, 

 who Tives the course of the axis as " east 10° N.," the build- 

 ing being to the southxvard or on the right of this line. 



I say nothing here of the protection afforded by another 

 building, which after the first moment, according to the hypo- 

 thesis of motion adopted by Messrs. Espy and Hare, was 

 constantly more or less to leeward of the building so protected. 

 By applying to Prof. Bache's plan, as before, a compass card, 

 moved from west to east without revolving, we shall find their 

 wind to commence nearly at east, passing thence through 

 south to south-west, and possibly to west-south-west, near 

 which it would terminate. Thus the first effects of the wind, 

 when, even upon the hypothesis of " suction," the building 

 was unprotected, could not produce the first motion in the 

 direction "to the west of north," which perhaps may be fairly 

 taken at 5" or 10° west of north ; and the wind, on their hy- 

 pothesis, would hardly appear to have reached a point which 

 could produce the second movement " to the east." 



I have been thus particular in this examination, because 

 the case thus alleged by Dr. Hare is a further specimen of 

 the erroneous inductions which have been made and relied 

 on by my opponents. In examining the plans referred to, 

 « See Journal of the Franklin Institute, vol. iii. third series, 1841, pp. 273 

 and 276; also American Phil. Trans., vol. v. 



