July 26, 1900] 



NATURE 



305 



12. i6h. lom. to I7h. lom. Moon occults k Piscium 



(mag. 5), 



13. 2oh. Venus at greatest brilliancy. 



15. Venus. Illuminated portion of disc = 0'28o. 

 15. Mars. ,, ,, ,, = 0*933. 



18. Saturn, Outer minor axis of outer ring = i8"*35. 

 18. I2h. 42m. to I3h. 24m. Moon occults i Tauri 

 (mag. 47). 



18. I4h. 47m. to I5h. 39m. Moon occults 105 Tauri 



(mag. 5-8). 



19. Mercury at greatest elongation (18' 32' W.). 



30. 22h. Venus in conjunction with moon, (Venus 

 i°49'S.). 



22. Jupiter 26' S. of ^ Scorpii. 



23. Ex 



pected return to perihelion of De Vico-Swift's 

 comet (1844- 1 894), 

 27, loh. 26m. ^Minimum of Algol (3 Persei). 

 New Variable in Herculis.— Prof, W, Ceraski, of the 

 Moscow Observatory, communicates to the Astronomische Nock- 

 richten (Bd. 153, No. 3650) the discovery of a new variable by 

 Mdme. Ceraski on photographs taken by M. S. Blajko. The 

 star's position is as follows : — 



R.A. Decl. Epoch. 



h. m. s. , // 



18 30 54-8 ... + 25 55 49 ... (1855-0) 



18 32 44-1 ... + 25 57 54 ... (1900-0) 



The star is not found in the B. D. At maximum the star is 

 slightly brighter than 9th magnitude, decreasing to a minimum 

 of about 1 2th magnitude. At present its brightness is increasing. 

 New Star in Aquila.— A telegram from Prof. Pickering, 

 Cambridge, Mass., dated 1900 July 9, states that the Nova of 

 the 8th magnitude found by Mrs. Fleming in April 1899 is now 

 a nebula of 12 magnitude. Its position is 



K.A. Decl. 



h. m. s. „ , 



19 15 16 ... -o 19 

 A further statement is made in the Aslronomische Nachrichten 

 (Bd. 153, No, 3651) that the measures are from the photographs. 

 Meteoritic Theory of the Gegenschein.— In the Astro- 

 nomical Journal, No 483 (vol. xxi. pp. 17-21), Mr. F. R. 

 Moulton puts forward a mathematical analysis of the conditions 

 which would appertain if the Gegenschein were due to the pre- 

 sence of a more or less condensed region of meteorites. The 

 idea of the problem appears to have been suggested by remarks 

 of Prof. Barnard (who has made consistent observations of the 

 phenomenon during the last sixteen years) to the author. 



Discovered by Brorsen about the middle of this century, very 



! few systematic observations are recorded until those of Barnard, 



I who has made careful determinations both of its position and 



I shape. He comes to the conclusion that it is always exactly 



opposite the sun, or as nearly so as can be determined. Other 



observers have stated varying positions, but in the case of so 



difficult an object it is advisable to consider the more systematic 



I records as having greatest truth. 



' After citing the well-known reasons for considering that inter- 

 planetary space is densely occupied by meteoric particles, mov- 

 mg with widely varying velocities in all directions, he supposes 

 that a great multitude will at any time be situated at the oppo- 

 sition point, and that a considerable proportion of these would 

 ; be under such initial (Conditions as to remain there for some 

 ^ lime. Then the meteors being very small compared with the 

 earth, they are treated as infinitesimal bodies, disturbing neither 

 the earth nor each other. He also neglects the eccentricity of 

 the earth's orbit. Then referring the motion of one meteor to 

 rectangular axes with the origin at the centre of gravity of the 

 sun and the earth, he traces the conditions for stability for a 

 certain time. Then by slightly varying the conditions, he finds 

 the nature of the movement of the infinitesimal body with special 

 reference to the circumstances under which it will make periodic 

 oscillations around certain points. The result of successive in- 

 tegration suggests that meteors passing near one of these 

 selected points with the assumed conditions of motion would be 

 j subject to forces directed nearly to this point, and would have a 

 ! tendency to revolve round it. Although after a few revolutions 

 , they might escape, the average result would be a condensation 

 I with respect to space, if not with respect to time. The difficult 

 point now to determine is whether a sufficient number would be 

 captured to become visible. If the meteors are revolving round 

 the sun at a distance of about 900,000 miles greater than the 



NO. 1604, VOL. 62] 



earth's mean distance, they will be moving slower than the 

 earth, which will gradually overtake them in longitude. As 

 they approach opposition they will be retarded and drawn in 

 towards the sun, their motion being thereby accelerated. The 

 net result of these actions will be to bring the meteors into the 

 plane of the ecliptic, thus causing the condensation at opposi- 

 tion, and explaining the tendency to an oscillation in latitude 

 which has been observed. 



Instead of being exactly opposite the earth, the point of con- 

 densation will be nearly opposite the centre of gravity of the 

 earth and moon, and consequently the Gegenschein should have 

 a monthly oscillation in longitude of the nature indicated by the 

 observations of Douglass, but much less in extent. The oscilla- 

 tion in latitude would, however, be monthly also, instead of 

 yearly, as the observations tend to indicate. 



A phenomenon, observed so far by Barnard alone, is the series 

 of marked changes to which the Gegenschein is subjected in short 

 periods of time, being large and round in September and the 

 beginning of October, becoming slightly elongated by the 4th or 

 5th, very much elongated by the loth or nth. and showing 

 merely as a swelling on the zodiacal band by the i8th. Although 

 this is not directly explicable, the shape of the Gegenschein will 

 depend oti the thickness of the zodiacal disc of meteorites, and if 

 the opposition point should pass through a dense portion of the 

 swarm it is readily conceivable that a change of form would 

 ensue. The distance of the opposition point works out at 

 930,240 miles from the earth. The period of oscillation would 

 be 183-304 days. It is thus suggested as possible that meteors 

 rnay move for long periods of time in the vicinity of the oppo- 

 sition point, in sufficient numbers to cause the faint glow of the 

 Gegenschein by reflecting the light of the sun. Reference is 

 finally made to a paper by M. Hugo Glyden in the Bulletin 

 Astronomique, Tome i, where similar views are enunciated. 



Meteor of July 17.— A bright meteor was seen in many 

 parts of the north of England on the evening of Tuesday, 

 July 17, shortly before nine o'clock. A few particulars con- 

 cerning the phenomena are given by correspondents in the 

 Yorkshire Post. An observer at Menston-in-Wharfedale saw ; 

 the meteor at a point about N.N.W. from that place, and 

 about forty degrees above the horizon. At Wiseton, Notts, 

 it was seen at 8.47, and at Bramhope at 8.48. At Armley, a 

 hissing noise was heard, and the meteor seen to disappear . 

 close by. 



THE GREAT EARTHQUAKE OF JUNE 12, 1897, 

 "T^HE investigation of the great earthquake of June 12, 1897, 

 being the most extensive of which there is historic record, 

 has naturally led to important additions to our knowledge. A 

 detailed report of this earthquake, by Mr. R. D. Oldham, has 

 been published by the Indian Government,^ and its investiga- 

 tion suggested a line of further research, the results of which 

 have been published in the Philosophical Transactions of the 

 Royal Society.^ The principal results described in these bulky 

 publications are here given in the form of an abstract. 



The known extent of the principal seismic area was about 

 1,200,000 square miles, a figure which will surprise many after the 

 statement that this was the greatest earthquake of which there 

 is historic record. One of the results of this earthquake was, 

 however, a re -examination of the records of the great Lisbon 

 earthquake of 1755, which has shown that the statements 

 regarding it, copied from one text-book to another, are grossly 

 exaggerated. The statement that it was felt in the lead mines ' 

 of Derbyshire is shown, by reference to the original record, to 

 be an error, the shock that was felt being clearly an independent, 

 local, though possibly sympathetic, shock. Apart from this, 

 there is but one doubtful record of its having been felt so far 

 north as England, though its effects were visible, both in 

 England and in Holland, in disturbances of the water in ponds. 

 The accounts of its having been felt in Iceland and America 

 refer to the sea-waves, which may travel to regions far beyond 

 the utmost limit at which the shock could be felt. Omitting 

 these records, taking only those which refer to the sensible 

 shock, and rounding off the seismic area to an elliptical form, it 



^ " Report on the great earthquake of June 12, 1897." By R. D. Oldham. 

 Memoirs of the Geological Survey of India, vol. xxix. 1899, pp. xxx + 379 

 + xviii ; 44 plates, 3 maps, 51 woodcuts in text. 



2 "On the propagation of earthquake motion to great distances." By 

 R. D. Oldham, Phil. Trans., Series A, 1900, pp. 135-174. 



