TRANSACTIONS OF SECTION A. 



579 



The folio-wing are the mean meteorological observations for the days of the two 

 sets of serial ohservations respectively : 



Mean temperature of air (F.) . 

 „ Cloud (0-10) 

 „ AVind Force (0-12) . 

 ,, „ Direction N. . 



N.E. 

 »» »» i» ■^» • 



„ ,, „ S.E. 



(1 » ). S. 



S.W. . 



,. „ „ N.W. . 



,, ,, „ Calms . 



The temperature of the air at the time of the afternoon observations was 82°-3, 

 and in the morning 78°'4, the difference, about 4°*0 higher, being nearly the 

 average difference at these times of the day of the temperature of the air over the 

 ocean where the climate is similar. The amount of cloud in the morning and 

 evening is virtually the same, and indicates that the observations were taken 

 under a sky having only a sixth part covered with cloud. The force of the wind 

 was also nearly the same, the mean force being just a little over 2 on the scale of 

 0-12, or, say, a light breeze, blowing at the rate of fourteen miles an hour. As 

 regards the direction of the wind, observations show that nearly the whole of the 

 winds at this season are west-north-westerly. 



The following figures, showing the depths in feet and the temperatures 

 (Fahr.), present the results of this inquiry in their simplest form : — 



Hence in the summer months the sun's heat penetrates to a depth of about 

 150 feet. At the surface the temperature in the afternoon is l°-4 higher than in 

 the morning, and this difference virtually holds to a depth of 16 feet. At lower 

 depths it gradually lessens to 0°-9 at 33 feet ; 0°-5 at 66 feet ; 0°-3 at 98 feet • and 

 vanishes at about 150 feet. Next morning the temperature is lowered to what it 

 was in the preceding morning, and so on from day to day, the loss during the night 

 being compensated by an increase of temperature on the following day equal 

 depth by depth, to the loss during the night. Thus at each depth the gain of tem- 

 perature from solar radiation is equal to the loss sustained by nocturnal radiation. 



9. Progress of the Magnetic Survey of the United States. 

 By L. A. Bauer. 



In 1899 it was my privilege to lay before this Association the plan, in accord- 

 ance with which a detailed and systematic survey of the United States had just 



p p 2 



