DISTRIBUTION OF ATMOSPHERIC MOISTURE. 483 



charge used on this occasion was sixteen pounds, lowered ten feet be- 

 low iive-feet ice ; its effect was the breaking up of a space of 400 yards 

 squai-e, besides splitting the ice in several directions. The last charge 

 would be equivalent to two pounds of " cotton gunpowder," but the 

 results with the latter explosive would, in all probability, be far more 

 effective. 



The work of an exploring expedition in the arctic regions for the 

 period of twelve months has now been detailed. No unforeseen acci- 

 dent, no detention in the ice, in fact no casualty of any description has 

 been taken into consideration, but every thing has progressed under 

 the most exceptionally favorable circumstances. That the same will 

 be the case with the Arctic Expedition of 1875 is too much to expect, 

 but that it will be successful in exploring a large area of unknown land 

 may be confidently hoped and anticipated. Geographical Magazine. 



-- 



DISTKIBUTION OF ATMOSPHEEIC MOISTUEE. 



ALL over the earth, the more largely where its beams reach the 

 surface with the least diminution of heat, the sun is continually 

 engaged in evaporating moisture from all exposed surfaces of water ; 

 this remains suspended in the atmosphere, and is carried about by the 

 winds in the form of impalpable vapor or of clouds, till the point of 

 saturation is reached, and the moisture falls again to the earth's sur- 

 face in the form of rain, or snow, or hail. Air becomes lighter, and 

 consequently expands and ascends, when it grows hotter, and becomes 

 heavier and falls with cold. The hotter it is the more moisture it is 

 able to hold in solution. Between the equator and the poles there is 

 a difference of 80 of average annual temperature. Li the torrid zone 

 the light, warm, vapor-laden air is ascending continually to the upper 

 regions of the atmosphere, and there flowing outward north and south 

 toward the poles, and the cold, heavy air from the polar regions comes 

 rushing along the surface to fill its place. As the seasons change, the 

 line of the greatest heat in the world gradually moves its position. At 

 the equinoxes of spring and autumn it runs along the actual equator, 

 or near it. In winter it lies south of the earth's equator, about mid- 

 way between the equator and tropic of Capricorn. Not more than 

 half as much of the tropic of Capricorn as of the tropic of Cancer runs 

 over land, and this makes a material difference, because the more sea 

 the more the intense heat is deadened and absorbed. In summer the 

 great continental area traversed by the tropic of Cancer, a long line 

 of which is removed from the ameliorating influence of the sea, be- 

 comes excessively heated, and from the great African Sahara, through 

 Nubia and Arabia to the north of India, runs a tract of intense heat, 

 in which the July average in the shade rises to 90. 



