668 THE POPULAR SCIENCE MONTHLY. 



the surface, may be lost. Again, if the surface be frozen, it may be 

 impossible for the water to percolate into the ground, and, though it 

 may descend in a more moderate manner, it may, in this as in the 

 preceding case, be lost. Obviously, there are many causes of the kind 

 which might be referred to ; these, however, are sufficient to indicate 

 the principle involved. 



We have shown that agricultural conditions do not perceptibly 

 affect the rainfall ; they do, however, very powerfully influence what 

 may be designated as the rain-waste. Thus, a growing plant vapor- 

 izes from its leaves an immense amount of water which its roots 

 have abstracted from the ground. A sunflower will thus remove 

 twenty ounces of water in a single day. There is in this respect a 

 waste which varies in the different months, being greatest in those 

 during which general vegetation is most rapid, and less in those the 

 winter months when it is torpid. For these and other such reasons 

 the monthly distribution of rain influences the actual supply. 



It is interesting to remark that the rainfall in New York greatly 

 exceeds that of London. Here it is 47.62 inches, in London it is but 

 25 inches, and the mean for all England is estimated at 31.25 inches. 



But these considerations of the amount of rainfall are only a por- 

 tion of a far more general and most important problem, viz. : 



Is the Climate of New York changing, or, more generally, is that of 

 the Atlantic States undergoing Modification ? 



In this case, as in the preceding, there is a popular belief that 

 clearing of land, drainage, and other agricultural operations, tend to 

 produce such a result. Land that has been ploughed and exposes a 

 dark surface to the sun, absorbs more heat, that is, becomes hotter, 

 than land covered with forest-growth. It does not seem unreasonable, 

 then, to suppose that, where thousands of square miles of surface have 

 been submitted to such operations, the corresponding effect should be 

 traceable, at least in the temperature of certain seasons of the year. 



Moreover, there are some interesting facts which are matters of 

 public observation and constant remark. Thus, as every one knows, 

 in the city of New York itself, there are no longer the deep snows 

 which characterized the winter seasons years ago. The large sleighs, 

 often drawn by very many horses, used in those times as the public 

 conveyances, have altogether disappeared from the streets. .It would 

 seem, therefore, that the winters have become milder. In like manner, 

 though in support of this conclusion we have less palpable evidence, 

 there is a very general opinion that the intolerable and long-continued 

 heats, which formerly made the summer months almost unbearable, 

 have greatly moderated, and, that, though the thermometer may oc- 

 casionally rise as high as it formerly did, the continuance of the hot 

 weather is shorter. 



