HAS OUR CLIMATE CHANGED? 673 



they strongly confirm the conclusion arrived at in those cases. Thus 

 the mean of the first series is substantially the same as that of the 

 third, being 55.39 and 55.51 respectively, though there is between them 

 an interval of seventy-three years. The mean of the second is sub- 

 stantially the same as that of the fourth, being 52.93 degrees and 

 52.48 respectively, their interval being seventy-six years; and it 

 may be especially remarked that the mean of the fifth series is very 

 nearly the mean of all the other four, theirs being 54.07, and its 53.34 

 degrees. 



Thus, again, we reach the same conclusion in the case of the city 

 of Charleston that we arrived at in the case of New York, Philadelphia, 

 and Boston, that the winter climate has not undergone any change. 



The general conclusion which this examination seems to warrant, 

 both as regards rainfall and winter climate, is this, that there has been 

 no change in the lapse of many years. None can be substantiated as 

 having occurred within a century. This proves that surface changes 

 through agriculture, drainage, etc., give rise to no appreciable meteor- 

 ological effect, and that the public opinion which asserts such an influ- 

 ence is altogether erroneous. 



Only recently have precise and correct views been entertained of 

 the progress of atmospheric changes. It is now known that cloudy 

 weather, or rains, or fluctuations of the barometer and of the ther- 

 mometer, are not of restricted or local origin, but that they have a 

 progress in a determinate direction, often of thousands of miles. This 

 fact is at the basis of the duties in which the Storm-Signal Corps is so 

 ably engaged. In many parts of the United States there are prairie 

 or treeless regions several hundreds of square miles in extent, yet these 

 are not rainless because they are treeless ; clouds drop water upon 

 them to the same amount that they do on the neighboring wooded 

 regions. Considerations such as these may satisfy us that the surface 

 modifications which the Atlantic States have undergone, since their 

 first settlement, have produced no meteorological effect, and that the 

 rainfall and winter probably remain the same, that they were many 

 centuries ago. 



I have restricted myself, in the foregoing climate examinations, to 

 the winter season, and have said nothing as regards the summer. Had 

 I done otherwise, it would have extended this report to an inconven- 

 ient length. Perhaps, however, what has here been substantiated, as 

 to the permanency in the cold of the winter, will be held as affording 

 strong presumptive evidence of a like permanency in the heats of sum- 

 mer, and that in these respects there is a mean degree which is main- 

 tained through indefinitely long periods of time. 



While such is our final conclusion, we must bear in mind that these 



mean or average results exhibit only one phase of the problem. They 



do not show the fact that there are brief cvcles of heat and cold, of 



moisture and dryness, following each other under the operation of 



43 



