186fi.] 225 [Chase. 



Brewster's neutral point was perceptibly more distinct than Babi- 

 net's at fifteen observations, and less distinct at two observations. 



I subjoin a few of my notes, which refer to points of special 

 interest: March 8th, S*" 45', P. M. Near the proper position for 

 Arago's neutral point, the positive and negative polarities coalesce 

 upon clouds, with no intervening space or neutral line. 



March 9th, G** 25', A. M. Hazy and polarization fluctuating. 

 lO*" 40', A. M. The polariscope showed a brilliant halo around the 

 sun, which I had not before noticed, but which was afterwards barely 

 visible to the naked eye. 12'' 10', P. M. Haze continues. Nega- 

 tive polarity remarkably distinct over the face of the sun, and for 

 several degrees north and south. 



March 11th, S*" 50', P. M. Sky covered with thin clouds. A 

 neutral point in the east, 42° above the horizon, and more than 70° 

 from the anti-solar point, with reversed polarization, or positive below, 

 and negative above. 5'' 25'. A similar point still observable, but 

 about 5° nearer the horizon. 



March 12th, & 30', A. M. Cloudy. Polarization positive from 

 east and west horizon, nearly to zenith. A similar observation was 

 made March 21st, at G*" p. M. 



March 17th, 9'' 15' and 10" 40' A. M.,* and March 18th, 10" 

 30', A. M.f Very clear. Sun so bright that I was unable to detect 

 the negative polarity between Babinet's neutral point and Brewster's, 

 even by screening the eye from the direct light of the sun. 



March 19th, 11" 5', A. M.| Halo, visible only through the 

 polariscope. 1" P. M. Snowing. 



March 20th, 5" 25', P. M. Cloudy. Polarization in horizon 

 everywhere positive. 



March 24th to 28th, inclusive. On each of these five successive 

 days Brewster's neutral point was remarkably distinct and beautiful. 



April 3d, 5" 40', p. M. Cloudy in west, and polarization positive 

 from zenith to horizon. 



Strong reflection sometimes changes the character of a compara- 

 tively weak polarization, from positive to negative, or vice versa. A 

 fainter reflection, by showing whether the bands are interrupted or 

 continuous, often aids in determining the character of the polariza- 

 tion. 



The increased refraction of a piece of glass, interposed between 



* On steamboat in Raritan Bay. f At Eagleswood, near Perth Amboy. 



j: In New York. 



