1902] THE ECOLOGY OF THE DELAWARE COAST 289 



lage is strongly impregnated with iron, showing that a stratum 

 of ferruginous material underlies at least part of the region. 



III. CLIMATOLOGY. 



A. Rainfall. — Besides lacking state geological and topo- 

 graphical surveys, Delaware has no Weather Bureau station, and 

 therefore the statements concerning the climate must be very 

 general. From the Rainfall Division of the U. S. Weather Bul- 

 letin, 1897, the following facts were obtained. The mean annual 

 precipitation is 40-50 inches in the Middle Atlantic states. The 

 distribution here is more uniform than in any other part of the 

 country, 20-25 inches being the usual amount in the growing 

 season (April-September), the least recorded for this period 

 being 10-15 inches. 



B. Heat and light. — -During the two months spent at Reho- 

 both a verj^ imperfect record of temperature and direction of the 

 wind was kept, and in the absence of accurate reports the results 

 will be used for comparison, The temperature figures for the 

 New Jersey and North Carolina stations were kindly furnished 

 by the U. S. Weather Bureau, the mean temperature for July and 

 August, 190 1, being as follows : 



July August July August 



Atlantic City, N, J. - 75 74 Cape May, N. J. - 75.6 7^ 



Rehoboth, Del, - jj,j 78.4 Cape Hatteras, N. C. 78.9 79.5 



Even on cloudy days the light on the coast is more intense 

 than inland, on account of the reflection from the sand surface, 

 while on bright days it is almost blinding. The amount of heat 

 radiated by the sand is considerable, and taken inconection with 

 the reflected light must necessarily have great influence upon the 

 flora, only those plants appearing that are able to adapt them- 

 selves to these severe conditions. 



C. Wind- — The direction of the wind, as well as its force, is 

 very important with reference to the shape and size of the dunes. 

 For the two months during which these observations were made 

 the prevailing wind was southwest, alternating with northeast 



J 



No observa- 



tions being made during the other months, no conclusions as to 



