MARYLAND GEOLOGICAL SURVEY 



169 



perature recorded in the history of the Baltimore station occi^rred on 

 the 10th, 7° below zero. On this occasion there was consequently an 

 inversion of temperature (a rise of temperature with elevation instead 

 of the normal fall) showing that the cold air occupied a relatively thin 

 layer near the ground. Maximum temperatures above 100° are not very 

 frequently observed at Charlotte Hall, though this figure was reached once 

 in June and once in July, 1893. also in July, 1898, 1900, 1902, and in 



Fig. 10.— The warm wave of August, 1900, at— (a) Charlotte Hall, (h) Grants- 

 vllle, (c) New Market. 



September, 1900. Temperatures below zero were also experienced in 

 February, 1895 (5° below zero on the Gth), and in January, 1899 (1° 

 below zero on the 2d). 



Duration of Warm Waves. 

 The maximum temperature exceeds 90° on the average 37 times per 

 annum at Charlotte Hall ; at Solomons only 20 times, showing the in- 

 fluence of the inland location of the former station. The record of 

 maximum temperatures is somewhat broken, so that the following table 

 of dates, on which the maximum was 95° or above, is not complete. 

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