MARYLAND GEOLOGICAL SURVEY 175 



the ocean exerted through the medium of the prevailing winds. The 

 effect of the winds is extremely important. The west coast of Europe is 

 subjected to the prevailing westerlies resulting from the circulation of 

 air about the permanent low pressure area in the vicinity of Iceland, 

 which brings the air from the ocean over the land. The conditions on 

 the eastern coast of the United States are quite different. We have the 

 ocean before us, but it cannot exert its full influence because the pre- 

 vailing winds are still from the west, from the land towards the sea. 

 In winter the Xorth American continent is covered l)y an area of high 

 pressure out of which air flows in all directions, giving Maryland its 

 prevailing northwest winds during the colder season of the year. In sum- 

 mer, it is true, the same region is occupied by low pressure, but the main 

 pathway of moving depressions being the Lake region and St. Lawrence 

 valley, Maryland is in such position as to receive chiefly southwesterly 

 winds in summer, which are also off shore. At some stations southeast 

 winds are found to prevail in early summer, but they are of feeble 

 character and do not transport air over the land from any great extent 

 of ocean surface. Consequently the waters of Chesapeake Bay and the 

 Atlantic Ocean cannot exert on the climate of Maryland the same marked 

 influence which gives western Europe its mild climate, and Maryland, as 

 well as all other States of the north Atlantic coast, retains a climate sub- 

 jected to great extremes, that is mainly continental in character. 



1 11 addition it must be observed that the Gulf stream is separated from 

 the coast of America, at least as far south as Hattcras, by the cold 

 Labrador current, which undoubtedly lowers the temperature of the 

 waters of the Atlantic near the coast below the normal. Referring to 

 the interior mass of water known as Chesapeake Ba}', it appears probable 

 that its temperature is also below the normal, since it receives a large 

 supply of cold water from melting snows and cold springs in the western 

 mountains, through the Susquehanna, Potomac, and other rivers. This 

 view is confirmed by the series of observations on the temperature of the 

 water surface in the harbor of Baltimore from 1882 to 1886, published 



