5.5 m. at totality, 6.0 m. at 1 hour after totality, 

 and 5.5 m. at sunset. 



In conjunction with these observations, baro- 

 metric pressure was measured from Wednes- 

 day, July 17 through Sunday, July 21 (fig. 2). 

 Totality coincided with the low pressure read- 



+ 1.0 



3000 



■..■I....I....I... ■!.... I,,..l,.,il..,.l.,,.l,... I 



1700 



1730 1800 



TIME (ed.l) 



1830 



ing (29.45 mm.) for the period of observation. 

 The consistent decline in pressure before the 

 eclipse and the rise after totality may or may 

 not be coincidental, but I have been unable to 

 locate similar records from other eclipses. 



Observations aboard the Rorqual in Bar 

 Harbor were supplemented by land-based ob- 

 servations on Mount Cadillac. LFE Electronics 

 (Boston) conducted a series of tests and sup- 

 plied me with comparative measurements of 

 a time-light series (fig. 3). The differences 

 among the curves are largely due to the dif- 

 ferent spectral responses of the photo cells and 

 filters. This information provided an inde- 

 pendent comparison of our own measurements 

 with the irradiance meter (table 2). Ten min- 



Table 2. — Surface and submarine illuminanre (luxes) during 

 the eclipse at Bar Harbor, Maine 



Figure 3. — Time-light curve from: A. photometer; 

 B. Gossen light meter; and C. Gossen Sixticolor 

 meter. (One foot-candle = 10.76 luxes.) 



' Totality 1745 e.d.t. 



utes before totality, the illumination at the 

 surface registered 4,000 lu.xes, the lowest value 

 in the series of measurements before and after 

 totality. Subsurface values were also lowest at 

 this time. As is evident from these data, the 

 eclipse occurred during a normal period of 

 declining brightness, but the substantial re- 

 duction in illumination at or near totality and 

 the subsequent increase clearly distinguishes 

 the influence of the eclipse. During the eclipse, 

 air temperature declined from 15.3° to 12.5° 

 C, and water temperature at the surface de- 

 clined from 12.8° to 11.3° C. Though the 

 eclipse may have accentuated the temperature 

 change, the late afternoon decline was antici- 

 pated. Water temperature at depth remained 

 nearly constant; 1 hour before totality it was 

 10.3° C. at 10 meters; 9.3° at 20 m.; 8.3° at 

 30 m. ; and 7.8° at 60 m. Salinity ranged from 

 31.35 to 31.74 %o at the surface and from 

 32.09 to 32.23 at 60 m. These differences 

 in salinity were assumed to be caused by tidal 



262 



U.S. FISH AND WILDLIFE SERVICE 



