March 28, 1901] 



NATURE 



525 



New Variable Stars. — Mr. Stanley Williams announces 

 the discovery of a new variable star in Perseus having the 

 position 



R.A. = 3h. 17m. 5i*8os.\, J, V 

 Decl. = +43°39'55"-6 j^'^SS)- 



The star is B.D. +43°726, catalogued as 8'9 magnitude, and 

 is in the same field as Nova Persei with a low power. 



The following magnitudes have been determined from photo- 

 graphs obtained with a 4 ■4-inch portrait lens. 



1900. Dec. 22 ... 1 1 '63 Mag. 



1901. Jan. II ... ii'47 



25 ... 1097 



Feb. II ... 10-87 



20 ... io"8o 



28 ... 10.53 



The visual magnitude of this star is considerably brighter thap 

 the above photographic measures. Espin classes the star R in 

 his " Stars with Remarkable Spectra." 



Dr. T. D. Anderson announces a new variable in Andro- 

 meda, whose position is 



R.A. = oh. 43-5m. l/,o.-, 

 Decl.= -f 33° 35' j(i«55)- 



The magnitude of the star has varied as follows : — 



Astronomische Nachrichten (Bd. 155, No. 3698). 



Light Curve of Algol.— Prof. A. A. Nijland, of 

 Utrecht, contributes an article to the Astronomische Nach- 

 richten (Bd. 154, No. 3695), containing the results of a 

 numerous series of determinations of the brightness of Algol 

 during its variation, and gives the light curve deduced there- 

 from. As shown, the variation is not symmetrical with respect 

 to the minimum, a break occurring on the passage from maxi- 

 mum to minimum. 



Chart for Observations of Nova Persei. — The first of 

 a series of charts for use in observations of Nova Persei has 

 been prepared by Father Hagen, of Georgetown College Ob- 

 servatory, and has recently been issued. The publication 

 consists of a map of the region surrounding the Nova, showing 

 stars down to the sixth magnitude, and a catalogue including 

 all the stars shown on the chart, with their actual magnitudes 

 and notes as to any peculiarities. A second series of charts is 

 in preparation, and will be issued shortly. 



PHOTOGRAPHY OF THE AURORA. 

 'T'HE ever-changing form, and the faintness, of the aurora 

 render this phenomenon a difficult subject to the photo- 

 grapher. Many have been the attempts to secure photographs 

 of what have appeared to be brilliant displays, but the results 

 have shown that little or no action had taken place on the 

 photographic film, in spite of the fact that very rapid plates had 

 been used. Herr Tromholt, who made a special study of the 

 photography of the aurora, exposed very rapid plates to what 

 he considered bright aurorse, and even with exposures from 4-7 

 minutes secured no trace of them. Later, at Christiania, he was 

 more fortunate, and obtained an impression with an exposure of 

 8 "5 minutes. To advance our knowledge of the changes in 

 form of this phenomenon, it is important that photographs 

 should be secured, if possible, in a few seconds, and not minutes. 

 This seems now to be feasible, judging from an interesting 

 account given in the Meteorologische Zeitschrifl (Heft 6, 1900), 

 by Herr O. Baschin. Herren Brendel and Baschin stayed 

 several months, during the winter of 1891-92, at Bossekop, in 

 Norwegian Lappland, to study the magnetic elements and the 

 aurora. 



For the photography of the aurora they employed an appa- 

 ratus belonging to Herr. O. Jesse, who had used this instrument 

 tor photographing luminous night clouds. The objective had a 

 focal length of 210 mm. and 60 mm. aperture; the dimensions 

 of the plates used, were 9 x 12 cm., the field photographed" 

 covering about 20° to 30". Schleussner's plates were employed, 

 and what appears to be the most important desideratum, the 

 plates were stained (with erythrosine) and thus rendered more 



NO. 1639 VOL. 63] 



sensitive to the auroral light. For the first experiments the 

 exposures given were comparatively long, namely three minutes, 

 but these were found to be excessive ; finally, seven seconds 

 were sufficient to give good pictures. The reproductions ac- 

 companying the account of these researches illustrate the results 

 secured with exposures of one minute and seven seconds re- 

 spectively. The latter is reproduced here and shows very 

 clearly the drapery-structure, although even this, according to 

 Herr Baschin, is overexposed, the structure having a watery 



hid. I. — Auroral-drapery on February r, 1892. 



and not sharp appearance. With such first results as these, 

 there seems no reason why, with plates stained to be most 

 sensitive to the particular colour of the aurora, and with the 

 most rapid lenses, even shorter exposures of a second or less 

 should not be given. 



A step in the right direction has, however, been made, and the 

 time is not far off when it will.be as possible to project the ever- 

 changing form of the aurora upon a screen as it is to exhibit in 

 this way the phenomenon of an eclipse of the sun. 



THE MISSISSIPPI RIVER. 



'T'HE Mississippi river, extending over a length of 2550 

 miles, has been placed by the United States Government 

 under the charge of a Commission, whose duties include the 

 making of a detailed survey of the channel from the headwaters 

 to the Gulf of Mexico ; a topographical survey showing the 

 natural and artificial features lying within a mile of the river ; a 

 system of Iriangulation with base lines along the stream ; longi- 

 tudinal and cross sections of the channels ; observations and 

 records as to floods ; and, for the assistance of future surveys, 

 the placing, at intervals of three miles, of permanent m%rks, 

 consisting of four stone or vitrified tile monuments placed in a 

 line normal to the stream, two on each bank, about half a mile 

 apart. Tne Commission has also the charge of the works 

 carried out for regulating and deepening the channel. 



Mr. J. A. Ockerson, who is a member of this Commission, 

 and who, in the year 1899, made a survey of the headwaters 

 of the Mississippi, contributed a paper on the subject to the 

 Proceedings oi ihe International Congress on Navigation held at 

 Paris last year,' from which the principal part of the informa- 

 tion here given has been obtained. 



1 "The Mississippi River: Some of its Physical Characteristics and 

 Measures employed for the Regulation and Control of the Stream." By 

 J. A. Ockerson, member of the U.S. Mississippi Commission Eighth 

 Navigation Congress on Navigation. Recorded in English and French. 

 (Paris 1900. _ 



