Intelligence and Miscellaneous Articles. 



543 



seen and determined, to judge at any rate from the publications on 

 this subject. We have had occasion to observe it on the summit 

 of the Righi (height 1800 metres) on the mornings of September 23 

 and 24, the height of the sun over the horizon being from 20° to 35°. 



On the 23rd, from 8 to 9.40 a.m., in remarkably fine weather, it 

 was easy to observe, by means of a Savart's polariscope, that in 

 the immediate neighbourhood of the sun, above as well as below, 

 the polarization of light was negative ; that is to say, that the plane 

 of polarization was perpendicular to the sun's azimuth. Below 

 the sun the fringes of the polariscope gradually diminished in 

 intensity, and disappeared at about 14° of angular distance ; a little 

 lower, inverse fringes were seen, the visibility of which increased 

 to the horizon. In order not to be dazzled we interposed an opaque 

 screen in front of the sun, or we placed ourselves in the shade of 

 the iron column of the balcony. 



Xext day the sky was less clear ; we have, however, been able 

 to repeat our observations. 



The angular distance of the neutral point is difficult to measure 

 owing to the feebleness of the polarization. "We have taken it by 

 determining by a sextant the height of the sun above the apparent 

 horizon, formed by distant mountains ; then measuring the distance 

 of the neutral point from the horizon by a special apparatus suffi- 

 ciently accurate to give angles to within 10' ; the middle of the 

 neutral space was sighted, which occupied about 4°. 



The 24th September, by the aid of this latter apparatus, we have 

 also determined simultaneously the distance of the neutral point 

 above the sun (Babinet's neutral point). 



The following are the numbers which we have obtained : — 



1 

 1888. 



Berne Time. 



Distance of the neutral point 

 from the Sun. 





Brewster. 



Babinet. 



September 23 



>» >> 

 j> >> 



I 24 



h m 

 8 5 

 8 17 

 8 25 



8 32 



9 40 

 8 5 

 8 12 

 8 15 

 8 25 



15 to 16° 

 17° 10 

 17° 20' 



16 20'* 

 15° (about) 

 16 



13° 



16° 40' 

 15° 48' 



15° 

 16° 



15 to 16° 

 15 to 16° 



These measurements for the distance of Brewster's neutral point 

 from the sun give very high numbers compared with those which 

 Brewster himself t and M. F. Busch i found. Is this a consequence 

 of the altitude at which the observations are made ? It would be 

 premature to assert this. — Comptes rendus, October 15, 1888. 



* Measured directly with the sextant. 



t Transactions of the Royal Society of Edinburgh, vol. xxiii., 1861. 



X Meteorological Zeitschrift for 1886. 



