268 Rotary Action of the Providence Tornado. 



prostrates fences, even in the path of a tornado. Besides, near 

 the center of such an inward blowing tornado, where only it 

 could act on these fences with lateral force, such winds must ne- 

 cessarily become neutralized both by blowing against each other 

 and by turning upward to escape, thus having little effect at this 

 point, within four feet of the ground. I say nothing here of the 

 possibility of any winds blowing with violence in such central 

 directions ; which I could never conceive : For the entire spaces 

 between the centripetal lines of arrows must be conceived as be- 

 ing filled by the affluent winds ; the lines only indicating their 

 directions. 



But on the other hand, let us suppose a strong whirlwind pass- 

 ing in the same direction : the front half of which, both on and 

 near the line pursued by its axis, must necessarily sweep laterally 

 across this line, first northwardly towards /, if it be revolving to 

 the left ; and the last half of the whirl on its arrival will sweep 

 southwardly towards e. That only the fence e was thus pros- 

 trated by the first wind of the tornado may be explained by the 

 protection afforded to / by the house, against the advancing 

 whirl, and perhaps here, also, by the spirally upward tendency 

 towards the center, in the wind which thus came round the 

 southeast corner of the house, prostrating e in its course. But 

 on the passing of the axis of the whirl, the wind would recur 

 with increased force from the opposite direction, upon the fence 

 /, prostrating it towards e ; while the latter, being already down, 

 and in turn partially protected by the house, would remain as it 

 first fell. 



In passing over the track of the tornado between Burr's house 

 and Providence river, several instances and groups of prostration 

 were observed. But owing to the open character of the grounds 

 throughout most of the track, the memorials afforded by the trees 

 were less frequent than have been seen in Other cases. 



Near the Pawtuxet turnpike, the tornado encountered a new 

 house belonging to Mr. Gardner. This house was in the south- 

 ern portion of the track on the right of the axis, and was re- 

 moved and turned several feet, towards the left. 



It is proper to mention here that the order of changes in the 

 wind's direction, viewing the tornado either as a whirlwind, or, 

 as claimed by Mr. Espy and seen in figure II, would at any fxed 

 point on this the right side of the track, be successively toioards 



