46 



BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



were then within a few miles of the coast; but they show that the 

 temperature remained 60°-61° until 8 A. M., then rose gradually to 

 67° at 1 p. M., July 16, at which time we were in Ipswich Bay. In the 

 afternoon we passed into the cold coast water off Portsmouth. The 

 air temperature for July loth shows a rise and fall roughly parallel 

 to that of the water, the latter, however lagging far behind the former. 

 On the 16th the air temperature rose from 64° at 6 A. M. to 76° at 

 11a. m., i. e., it was roughly parallel to the rise of the water. 



On August 7th we had a second opportunity to observe diurnal 

 warming of the surface. This day was flat calm, with a bright sun, 

 but slightly hazy. We ran all day southeastward from Cape Eliza- 

 beth. Close to the coast, of course, we passed through the cold band; 

 but at 9 A. M. we had run into the warm off-shore water, some fifteen 

 miles from the Cape; and air and water temperatures for every hour 

 from this point on until midnight are plotted (fig. 5). The surface 



Fig. 5. — Air and surface temperatures, August 7, 1912. 



temperature rose steadily from 60°, until at 1 p. m. the maximum, 67°, 

 was reached. By this time the air temperature had risen only 1° 

 (from 63°-64°) ; but by 3 p. m., when the water had fallen to 64°, the 

 air reached its maximum for the day, 66°. From this time onward 

 both air and water cooled, until at midnight both were 61°. This 

 case is especially interesting, because the warming of the water pre- 

 ceded that of the air, and reached a higher degree. So far as they go, 

 these observations show that diurnal warming in the region in question 

 is very considerable in clear, calm weather, even as much as 6° or 7°, 

 but it is usually much less, i. e., 2° to 3°. 



