436 SCIENTIFIC RECORD FOR 1882. 



region between W^ and 20° region, tlie common arc must be in tbe zen- 

 ith, but this bght is so small in comparison with the ray aurora, that it 

 must draw but little attention. The fourth region is a belt between 20° 

 and 28° distant. Here the aurorte usually begin with a luminous bow 

 in the magnetic north, out of which spread radiant beams either into 

 free space or to another ring. The Jifth region lies between 28° and 3G° 

 distant ; the interior circles of the glory are not seen in this region. 

 {Nature, XXV, p. 372.) 



Weyprecht, shortly before his death, published a "Pactical Introduc- 

 tion to the Observations of i^urorie," &c. (Vienna, 1881), in which he re- 

 j)eats the important classification of auroral forms given in his Nordlicht- 

 Beobachtungen. For observations on' the altitude of aurora), with a view 

 to calculation of height, he recommends a simple instrument, consisting 

 of a tube with an eye-piece, movable in a magnetic meridian, and with 

 an altitude circle reading to ^°. The tube must be attached to the 

 end of the axis, so as to be capable of sweeping the entire meridian. 

 The observations should be repeated at short and regular intervals, and 

 both the ui^per and lower edges of the arches should be observed, thus 

 giving at once the mean altitude and breadth of the bauds. If the 

 "dark segment" is visible, its mean height and the azimuth of its sum- 

 mit must be observed, as it probably indicates the direction of the origin 

 of the aurora. If a corona is formed the approximate position of its 

 center must be observed. Another method of determining the position 

 of the corona is by measuring the direction of the rays of which the 

 arches are formed. This is best done by measuring their inclination 

 from the i)erpendicular in two azimuths 90° apart. If the tube we have 

 mentioned be provided with an azimuth circle and cross- wires in the 

 eye-piece, with a position circle reading to ^°, this is readily accom- 

 plished, the perpendicular being verified by observation of a plumb 

 line. {Nature, July, 1881, xxiv, p. 211.) 



The aurora was remarkably frequent at Stykkisholm, Iceland, during 

 the winter of 1880-81. From September 5, w^hen the first aurora of the 

 season was observed, to February 28, to which date the observations 

 have been received, aurorae were seen on forty-five nights, viz, five in 

 September, eleven in October, four in ISTovember, eight in December, 

 twelve in January, and five in February, the phenomena being very 

 brilliant on September 29, December 23, January 31, and February 5. 

 {Nature, July, 1881, xxiv, p. 261.) 



Prof. Sophus Tromholt has published the results of a discussion of 

 839 observations of the aurora borealis, at 132 Scandinavian stations 

 on 154 nights, between September, 1878, and April, 1879. These obser- 

 vations are classified under four heads in accordance with (1) longitude 

 and latitude of stations; (2) time of year and age of moon; (3) color, 

 altitude, and form of streamers; (4) sound. Herr Tromholt considers 

 that it may be accepted as certain that the aurora is a losal phenome- 

 non, circumscribed by narrow limits, and manifested at inconsiderable 



