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H. A. Hazen— Tornadoes. 181 
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Art. XXITI.—Tornadoes ; by Henry A. Hazen. 
“THE true tornado,” says R. H. Scott, ‘occurs off the west 
coast of Africa and is identical with the arched squall of other 
* waters.” This restrictive definition of a tornado is not accepted 
generally in the United States, where it is applied to an intense, 
seemingly local, outburst, ordinarily preceded by a funnel- 
shaped cloud, having a rapid rotation and a more or less slow 
up-and-down movement. The better designation would un- 
doubtedly be “ whirlwind,” but the term tornado has become so — 
well understood that it hardly seems wise to attempt a change. 
e importance of a proper study and a good knowledge of 
the forces, which underlie the formation of a tornado, will be 
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as already recommended, some more general means be em- 
__ ployed for destroying or diminishing the force of the storm as 
_ it approaches a large city. Such an idea may seem chimerical ; 
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t is the object of this paper, first, to set forth some of the 
ordinary theories that are advanced for explaining the origin 
and development of these outbursts; secondly, to show some of 
_ the seeming difficulties in these theories; and thirdly, to point out 
_ a few of the characteristics of these outbursts and to attempt to 
show lines of investigation upon which.a further advance may be 
_ Made toward a true knowledge of the forces eae them. 
Unfortunately, their origin is involved in much obscurity, 
due in part to a lack of observation of the conditions imme- 
diately preceding the sudden and destructive manifestations. 
_ The following quotations from authorities will suffice to show 
some of the views at present entertained. One writer says: | 
_ “The inward rush of winds toward a depressed center is the 
_ cause of our thunder-storms, which are only infant cyclones and 
tornadoes. The whole country for 500 miles square from the 
Missouri to the Ohio valley is covered with a mass of warm moist 
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