CURRENTS OF AIR. 101 



CURRENTS or AIR. 



The current which prevails most in all that part of the state 

 lying south of the summit level between Lake Erie and the 

 Ohio river, comes from the Mexican Gulph. This current fol- 

 lows the Mississippi upwards, and the Ohio river and its tribu- 

 taries, to their sources, where it comes in contact with a cur- 

 rent of air descending the lakes, from lake Superior and the 

 Frozen Ocean. These two currents having united their for- 

 ces, pass down lakes Erie and Ontario, and through the St. 

 Lawrence to the sea. Where these two currents meet, va- 

 ries from forty miles south, to as many miles north of the sum- 

 mit level, between the waters of the Mississippi and those of 

 the St. Lawrence. At the town of Delaware we have often 

 seen both these currents, bearing along the clouds. Some- 

 times one current was uppermost, sometimes the other, as ei- 

 ther set of clouds happened to be the most loaded with mois- 

 ture. When those two currents of air impinge on each other, 

 meeting at an oblique angle they both move with a very great 

 force, A tornadoe, is the necessary result. Such an one 

 touched Urbana, and rising, swept across Licking and Knox 

 counties, a few miles below Kenyon college; then rushing 

 along eastwardly, touching New Lisbon in Columbiana county, 

 it passed onward, occasionally touching the earth, until it rose 

 over the Alleghanies, and we heard of its ravages no farther 

 in the United States. Across Licking and Knox counties its 

 width was scarcely one mile, but where it moved, it prostrated 

 every forest tree, or stripped it of its limbs and left it stand- 

 ing as a monument of its inexorable wrath. This tornadoe hap- 

 pened on the 18th of May, 1825. 



On the other or northern side of the summit level, before 

 mentioned, there was such a tornadoe in the year 1788, and it 

 passed the Maumee river, about five miles below the head of 

 the rapids, and moved eastwardly quite across the now state of 

 Ohio, occasionally touching the earth and prostrating the forest 

 wherever it descended to the ground. 



Another effect, resulting from the impinging of these two 



