cxxu 



the pressure of the atmosphere from the barometer. Hence the law of 

 storms says the winds blow from all sides towards a point where the ba- 

 rometer is low. 



Again, the upward current of air in the centre of a vortical whirl carries 

 up the warm moisture-laden atmosphere, which immediately becomes con- 

 densed, and a fall of rain or hail occurs. But, again, the condensation of 

 vapor into rain-drops is accompanied by the evolution of heat, and this 

 heightens the momentum of the ascending current. Hence the tendency 

 of a small vortical movement in the atmosphere is to expand into a general 

 cyclone. The ultimate result of the cyclone or storm is to restore an equi- 

 librium between the upper and lower strata of the atmosphere in regard to 

 temperature and moisture; the storm proceeds until the upper stratum has 

 become warmer and more moist, while the lower stratum has become cooler 

 and less charged with moisture. The vast movements of the air between 

 the equator and poles to restore the equilibrium act continually to produce 

 a tension between the upper and lower strata of air, and thus give occasion 

 to the ever-recurring cyclones. Another remarkable feature in the theory 

 of storms takes note of the fact that while there is more water in the South- 

 ern hemisphere than in the Northern, yet there is less atmosphere. The 

 cause of this has been shown, mathematically, to be found in the fact that 

 in the Northern hemisphere, where there is more land and more numerous 

 and lofty mountain chains, the resistance to the deflecting tendency which 

 arises from the earth's rotation is greater than in the Southern hemisphere. 

 The consequence of the more rapid and regular movement of the winds in 

 the Southern hemisphere is a greater depression there. The trade-winds 

 blow from the Southern hemisphere with greater velocity and momentum, 

 and overcome the northern trade-winds, forcing them several degrees north 

 of the equator, permanently. 



The subject of Meteorology, considered in its more general aspect, is 

 one that influences many important phases of human interest. In some 

 remote future, when the air-currents ^re thoroughly understood, aerial 

 navigation may become entirely practicable. Even now, when so few of 

 the conditions are known that the weather can be foretold for scarcely one 

 week in advance, our commercial marine is greatly benefited. When it 

 becomes possible to forecast the season for one or three months ahead, the 

 farmer will be provided with the means to avoid the uncertainty attendant 

 on his vocation. "Scientific agriculture" may then exist as a fact as well 

 as in name. 



Next among the important items which the scientific interest of the new 

 year brings to mind is the approaching transit of Venus. On the 8th of next 

 December occurs the first transit of Venus that has occurred since the im- 

 provement of the telescope. It is one hundred and five years since the last 

 one took place. Extensive preparations are making in this country and in 

 Europe for the most accurate mathematical verification of the several ele- 

 ments of the phenomenon. The moment of contact with the limb of the 

 sun, if fixed accurately from different points of observation, will settle the 



