ELISHA MITCHELL SCIENTIFIC SOCIETY. ^1 



per cent. ; barium = 1. 12 per cent. The percentage of copper in tlie 

 mormal acetate is 34.49. 



According to Watts the acetate of copper and calcium is prepared 

 t)y simple evaporation at 25"^ — 27^ c. of the mixed (in molecular pro- 

 portions) solutions of the two salts. It would seem from these ex- 

 periments that the barium double acetate cannot be gotten in the 

 same way. The tendency to form a double salt of copper and 

 barium is not so great as in the case of copper and calcium. Time 

 was lacking for a further examination of the subject. 



Chemical Laboratory U. N. C, May, 1884. 



A THEORY OF TORNADOES. 



J. W- GORE. 



Tornadoes are phenomena accompanying a great disturbance of 

 the atmospheric eciuilibrium. A centre of minimum pressure travels 

 across the continent, say in a northeast direction, and any where 

 south and east of its track tornadoes may occur. This centre of 

 low pressure produces and tends to produce a cyclonic movement of 

 the air over a large area of country. The wind to the south and 

 east will be southwest, warm and moist. Suppose a given area to 

 be within the region of the cyclonic currents, which are from the 

 north and west and therefore cold and dry. The meeting of these 

 winds of different temperatures and hygrometric states will cause 

 condensation, liberation of heat and a consequent fall of the barom- 

 eter. Thus a cloud will be formed, gradually extending southward, 

 for simplicity we will suppose this cloud to be bounded on the south 

 by an»east and west line. Along this line the air is rarified, thereby 

 accelerating the southwest wind and causing the air on the north 

 side to move towards this line, the slowl , moving cyclonic current 

 giving an eastern component of motion ; hence it will be a w ind 

 west of north. The condensation of moisture will thus be increased 

 by the accelerating and producing of those winds, and in their turn 

 these velocities will be augmented until they attain considerable 

 violence. 



