THE TORNADO OF 1851. 171 



Stood appalled before llie exhibition of such wondrous power, scientific men sought to 

 explore its mode of action, and to find there a corroboration or a refutation of their pre- 

 conceived views. It was in obedience to the call of many of this latter class, that 1 

 undertook the survey whose results are embodied in the accompanying map. 



It is not my object, in this memoir, to present any new theory upon the subject, nor 

 even to indulge in any speculations of my own, but simply to record the facts observed, 

 and to state in the plainest manner possible how the survey was made, in order that 

 those who study the map may know just how much confidence is to be placed in its 

 indications. This appears to me the more necessary, for the reason that, heretofore, the 

 tracks of tornadoes have not generally been surveyed. The most that is ordinarily 

 attempted is a rapid and rough reconnaissance of the ground, which, from its very 

 nature, can embrace only the most prominent general characteristics, and is moreover 

 extremely liable to be warped and biassed by the opinions and theories of the observer. 

 It was sufficiently evident to me, in the course of the present survey, that had I gone 

 upon the ground to make a simple reconnaissance of this kind, selecting spots here and 

 there upon which to devote my principal attention, I could have found ample corrobora- 

 tion of almost any of the many previously existing theories, as well as of the new ones 

 to which this particular tornado has given birth. The effect of local causes is so great, 

 that any examination, to be worthy of credit as a test, must embrace, not isolated spots 

 selected here and there, but a continuous track, in which all the varied circumstances of 

 woods and plains, hills and valleys, villages and cultivated fields, may appear in their 

 proper succession. We may even go farther than this, and assert that the law of a 

 storm's action may often be deduced, not so much by examining what has really suffered 

 and been prostrated in its course, as by turning our attention rather to those parts, which, 

 lying as it were in the very jaws of destruction, have yet escaped unscathed. 



It will be seen, by referring to the map, that it embraces only that portion of the track 

 included between the foot of Wellington Hill, hi Waltham, and the Mystic River. It will 

 be a source of regret with many, that the particular portions in which they are most 

 interested are not to be found on the map. To such I can only say, that, had sufficient 

 time been at my disposal, I would most gladly have traced out the whole course from the 

 beginning to the end. And this would have been the more satisfactory, inasmuch as 

 opinion is by no means settled as to the point either of commencement or ending, — 

 some persons asserting that its terminus was in Maiden, while others, with equal con- 

 fidence, maintain that it went out to sea. As a limited portion only could be examined 

 within the time which was at my command, I have seen no reason to be dissatisfied 

 with the selection which was actually made. A previous reconnaissance had assured me, 



