264 THE PLANT COVERING OF OCRACOKE ISLAND. 



SUNSHINE. 



The observations cover a period of nearly thirty years. Normal 

 annual sunshine,^ stated in percentages of possible sunshine, 54, as 

 compared with 52 at Cape Henry, 51 at Norfolk, and 52 at Wilming- 

 ton. The monthly percentages are as follows: 



Month. 



January 

 February 

 March .. 

 April 



Per 

 cent. 



Month. 



May — 

 June . . , 

 July... 

 August 



Per 



cent. 



Month. 



Per 



cent. 



September 

 October... 

 November 

 December 



Normal annual sunshine, stated in Irours, 2,392.2, as compared with 

 2,314.G at Cape Henry, 2,270.1 at Norfolk, and 2,312.7 at Wilmington. 

 The normal monthly number of hours of sunshine are: 



1 



These records yield the result that the normal annual percentage 

 of sunshine is low compared with that in much of the territory of the 

 United States, especially west of the Mississippi River; but it is not 

 much less than that prevailing in other parts of the Southeastern 

 States, while it exceeds the percentages given for the northern portion 

 of the Atlantic slope. 



ATMOSPHERIC HUMIDITY. 



This is stated in percentages of possible saturation, which of course 

 varies at different seasons with the temperature, etc. Annual (for a 

 period of seven years), 81.4 as compared with 74 at Cape Henry, and 73 

 (during nine years) at Norfolk and Wilmington. Monthly, as follows : 



Month. 



Per 

 cent. 



January . 

 February 

 March — 

 April 



Month. 



Per 

 cent. 



Month. 



May — 

 June ... 

 July.... 



August 



September. 



October 



November. 

 December . 



Per 

 cent. 



The annual percentage thus shown is greater than that recorded 

 for any other station in the United States, excepting those in the 



' These figures only approximate the real values. They are derived from statis- 

 tics of cloudiness. 



