THE WEATHER, AND WEATHER PROPHETS. I55 



minutes on a surface perpendicularly exposed to it ; and 

 from this he will have no difficulty in calculating the 

 depth of water over the whole area of the globe, land 

 and sea, per annum, which it would suffice to convert 

 into vapour if wholly expended in so doing. This he 

 will find to amount, as nearly as may be, to nine feet* 

 IVIeteorologists, collecting the registers of "rainfall" in 

 all regions of the globe, and comparing and calculating 

 on their indications, have come to the conclusion that 

 taking one region with another, the quantity of water 

 actually precipitated from the air per annum, in the 

 forms of rain, hail, snow, and dew, would suffice to 

 cover the whole of its surface to a depth of five feet. 

 Remains the eqiiivalent of four feet, expended in warming 

 tlie soil ; which is partly radiated away, and partly com- 

 municated to the air, thus going to maintain the average 

 temperature, according to its climatic distribution. And 

 as solely expended on this last-mentioned object, we 

 have to reckon fully one-third of the sun's total radia- 

 tion, or one-half of that already accounted for, which is 

 absorbed by the air, or rather by the moisture in it, 

 before reaching the earth. The joint effect of these 

 two portions is, as we have seen, to maintain the air in 



* We will make the calculation for him. An inch of ice melted 

 in 2 hours 13 minutes over a great circle of the globe perpendicu- 

 larly exposed to the sun, corresponds to a quarter of an inch in 

 that time over the whole surlixce (which is four great circles), or, 

 per annum, to 9S775 inches ; or to nine-tenths of this, or 8go inches 

 of water raised 135 Fahr. in temperature; or (taking the initial 

 temperature of the water evaporated on an average at 60 Fahr.) to 

 loS inches or 9 feet heated iii2 to convert it into steam. 



