Rotary Action of the Providence Tornado. 



267 



The barn g and the shed h were destroyed, and the materials swept off toward 

 the first named buildings. A corn-house, standing on the same side with the barn, 

 is stated in the Providence papers to have been blown over to the west, but I can 

 find no notes of my own respecting the direction of its fall. 



The effects here exhibited appear to me to be due to a pro- 

 gressive whirlwind, revolving to the left ; for we may notice, 

 as in the New Brunswick tornado, a more onward direction in 

 the trees prostrated on the right of the axis, d, m, n, o, &c., than 

 on the left side ; while the outermost prostrations on the right, 

 n, 0, point still more nearly than the average on this side, to the 

 course of the tornado : And on the left side of the track we have 

 the tree A; in a direction inclined several degrees backward from 

 the course of the storm. The value of these indications of whirl- 

 ing action I have endeavored to point out in my remarks on the 

 New Brunswick case. [This Journal, Vol. xle, p. 70-75.] 



At the front of the house a, however, were two slatted door- 

 yard fences, extending from the house to the road. The fence e 

 was overthrown northward toward /, and the fence /in the con- 

 trary direction towards e : both directions being transverse to the 

 line of the axis, which passes between them. Such cases have 

 been adduced as supporting a directly inward course of the wind 

 in the body of the tornado ; or, as indicating two bodies of oppo- 

 sing wind meeting on a central line ; but I draw a different con- 

 clusion. 



Let Fig. II represent, Fig. Ii. 



horizontally, the direc- 

 tions of such center 

 blowing winds in the 

 body of the tornado, 

 and let it be supposed 

 as passing over the area 

 of Fig. I, without re- 

 volving, so as the course 

 of the center will coin- 

 cide with the arrow 

 which indicates the 

 course of the axis on 

 that figure. It may thus be seen that on this hypothesis the 

 wind must strike the fences e, /, either parallel to their length, 

 or but little oblique ; a direction of wind which seldom or never 



...V,- 



