LOCAL CLIMATOLOGY. 77 



Were it not for the softening influence of these lakes, it can 

 hardly be doubted that our winters would be on the average at 

 least ten degrees colder than the}^ now are, or as cold as they are 

 in Asia just east of the Caspian sea, where there is a gap in the 

 great mountain chain between the Caucasus and Hindoo Cush, in 

 what are known as the plains or steppes of Mayntsch, where the 

 average temperature for the three Avinter months, December, Jan- 

 uary and February, is only 15 deg. above zero, and periods are 

 not unfrequent with the thermometer 25 deg. and 30 deg. below 

 zero for several days in succession. But owing to the influence 

 of these inland lakes, we have along their border and around 

 them, spring as early, autumn frosts as late, and winter as mild, as 

 in central Pennsylvania ; while in the region along the south boun- 

 daries of New-York and in the northern tier of Pennsylvania 

 counties, the summers are some two or three weeks shorter, and 

 the winters several degrees, five or six, colder. 



Besides the foregoing general principles, there are many details 

 of local climatolog}^ that can be obtained only by long-continued 

 and careful observations in each place ; and such ol)servations, 

 when published in large numbers and from a large number of 

 places, will undoubtedly furnish facts from which further gene- 

 ralizations and laws can be deduced. But the observations should 

 be published in full : no abridgment or summary will answer. 



As illustrating what I mean, I will refer to a generalization 

 partially made by myself, and arrested in its progress towards 

 completion for want of the very material I have referred to. In 

 summer we often have days of great intensity of heat ; and in win- 

 ter, in like manner, days of greater cold than mere astronomical 

 forces can account for. Now, whenever we have had, at Geneva, 

 a day in which the thermometer has fallen to six or seven degrees 

 below zero, or more, I have found the following phenomena, 

 observed here. First. The wind has always passed from a south- 

 westerly direction to west, northwest, north, northeast, and in 

 nearly if not quite all cases it passed by way of east round to 

 southwest again ; and if it were blowing very stong, as happens 

 in about half the instances, when it started from the southwest, 

 it gradually lulled down and became very slight as it reached 

 north. Secondly. The barometer commenced rising as the wind 

 beo^an to chano^e and the cold to increase, and continued to rise 

 until it reached a very high point. Last winter it reached the 



