240 



Mean Direction of the Wind. 



of temperature over neighboring portions of the earth's surface ; and 

 that at Wallingford, as well as at Toronto, the great changes in the 

 warmer months are due to the proximity of a large surface of water. 

 The diurnal change at Wallingford cannot be ascribed simply to the 

 inequalities of the earth's suiiace. This cause might aftect the mean 

 direction of the wind, but could not produce a change in the Avind's 

 dii*ection from hour to hour. Moreover, the facts stated on page 209, 

 show that the horizon at Wallingfoi'd is but little obstructed by hills ; 

 while the great regularity in the changes shown by the curves on 

 Plate VIII, indicates that the inequalities of tlie earth's surface do 

 not here greatly aifect the wind's direction. 



We propose, then, to inquire whether the diurnal changes in the 

 direction of the wind at Wallingford, can be explained by the influ- 

 ence of the diflerence of temperature of the land and the neighboring- 

 water. For this comparison we will take the temperature of New 

 Haven as the standard for the temperature of the land at difterent 

 pei'iods of the day and year, and for the water we will take the 

 numbers derived from Maury's thermometrical charts of tlie Atlantic* 



In Table VI, column second shows the mean temperature of the 

 diffei'ent months at New Haven; column third shows tlie mean tem- 

 perature of the warmest hour of each month ; and column fourth 

 shows the mean temperature of the coldest hour of each month. 



Table VI. — Temperature of N'e^o Haven and Ocean, compared. 



Column fifth shows the mean tempei-ature of the Atlantic Ocean for 

 a zone extending a little over a degree on each side of the parallel of 

 New Haven, Hind reaching eastward to longitude 69° ; while column 

 sixth shows the mean tem))erature of that portion of the Gulf Stream, 

 which is comprehended within the limits of the same zone. The 

 diurnal change of temperature of the water is not accurately known, 

 biit is presumed to be less that half what it is at New Haven. The 

 distance from Wallingford to the nearest point of the Gidf stream 

 is about 300 statute miles ; its distance from the nearest point of the 

 Atlantic Ocean is about 50 miles ; but Long Island Sound, which is 



* Maury'.s wind and current charts, Thermal sheets, Series D. 



