CLIMATE. 13 



4.- CLIMATE. 



The climate of the Adirondack Wilderness varies greatly with the 

 season. Snow covers the ground from some time in November till 

 the middle or latter part of April, and in mid-winter averages over 

 four feet in depth on the level. During this period the mercury 

 often falls below — 25^ Fahr. ( — 32^ C), and more than once it 

 has been frozen ( — 40^ F. and C.) In summer the days are warm 

 and the nicrhts cool. Owino^ to the altitude of the recrion its mean 

 annual temperature falls considerably below that of the surrounding 

 country. Guyot says : " On an average an increase of three hundred 

 and thirty feet of altitude diminishes the temperature one degree 

 P""ahrenheit; hence the rate of diminution is about diree degrees to 

 every thousand feet." Therefore the temperature at the summit of 

 Mt. Marcy should average sixteen degrees Fahrenheit below that of 

 tide-level in the same latitude. Mr. Verplanck Colvin found, from 

 observations made at three sets of localities, in 1876, that the mean 

 decrease in temperature per each thousand feet increase in altitude, 

 in this region was 2.93° Fahr. in August, 4.1 1'^ F. in September, and 

 4.52° F. in November.'-' On this basis the mean temperature of that 

 portion of the Adirondacks having an altitude of four thousand feet 

 (1,2 19.20 metres) would average below that of New York city during 

 the same time, 11.72° F. in August, 16.44° I'- ^^ September, and 

 18.08° F. in November, if in the same latitude. 



There are probably few places on this continent that are subject to 

 greater or more sudden changes of temperature than this area. Vari- 

 ations of forty, fifty, and sixty degrees Fahrenheit, during the twenty- 

 four hours, are by no means uncommon; andT have seen the mercury 

 fall over seventy degrees Fahrenheit in fifteen hours in winter. My 

 journal records a rise of 42° in six hours, of 32° in five hours, and of 

 12° in one hour; a fall of 38° in thirteen hours, and one of 20° in four 

 hours. These great and rapid changes usually occur in winter — dur- 



* Report of Adirondack Survey, Verplanck Colvin, Superintendent, iSSo, pp. 324-6. 



