May 1 1, 1905] 



NATURE 



OUR ASTRONOMICAL COLUMN. 



EniEMERis FOR CoMET 1905 a. — A set of elements and a 

 daily ephemeris for comet 1905 a are given in No. 4011 of 

 the Astroiwmische Nachrichten. The ephemeris has been 

 computed by Herr M. Ebell, and an extract is given 

 below : — 



Ephemeris 12/1. {ALT. 



din). 



h. 



. (true) 



5 (true) 



Bright 



May 12 ... 9 45 27 ... +49 158 ... 0-1066 ... 9'98i4 ... 0-42 



16 ..10 8 56 ... +49 44 '2 ... 0'ii72 ... O-O002 ... 0-36 



20 .. 10 31 29 ... +49 5i'5 ... o'r28i ... o'oiSg ... 0-32 



24 ... 10 52 58 ... +49 40-1 ... 0-1394 ... 0-0375 ... 0-28 



28 , . II 13 II ... +49 13-1 .. 0-1508 ... 00558 ... 0-24 



Tune I .. II 32 9 ... +48 32-8 ... 0-1623 .. 0-0740 .. 0-21 



5 ... II 49 51 ... +47 41-8 ... 0-1739 .. 0-0919 ... o-iS 



Comets 1905 II (1904 e) and 1904 I. — A daily ephemeris 

 for comet 1904 e, computed by Dr Stromgren, is given in 

 No. 401 1 of the Astronomische Nachrichten. The comet is 

 now very faint, and as seen by Dr. Palisa at the be- 

 ginning of April it was 10" in diameter, and had a four- 

 teenth-magnitude nucleus. During the present month it 

 will apparently travel through the constellation Lynx in a 

 south-easterly direction towards Leo Minor. 



A bi-daily ephemeris for comet 1904 I, computed by 

 Herren Nijland and van d Bilt, is given in the same 

 journal. This comet is also faint, being 0.052 as bright 

 as when first discovered, its magnitude then being about 

 q.o. It is likewise situated in the constellation Lynx, and 

 is apparently travelling in a S.S.E. direction towards 

 Cancer, although at the beginning of .September it will 

 only be about 3° south of 35 Lyncis. 



Observ.ations of Jupiter. — The results of their observ- 

 ations of Jupiter during the 1904-5 opposition are given 

 bv MM. Flammarion and Benoit in the May number of 

 the Bulletin de la Societi astronomiquc de France. 

 Numerous points of change in the colours and forms of the 

 various features are noted, and some of them are illus- 

 trated on the four drawings accompanying the article. 

 .•\mong the other conclusions derived from these observ- 

 ations the writers state the following : — (i) the estimations 

 of the coloration of the equatorial bands do not confirm 

 Mr. Stanley Williams's views as to periodical changes 

 therein ; (2) the appearance of the Great Red Spot has 

 not changed since the previous opposition ; (3) the large 

 variation of the longitude of this feature between March 

 and June, 1904, was probably due to the passage alongside 

 it of the dark region of the tropical zone; (4) a clear spot 

 situated in longitude 0° of system ii., and dividing the 

 south equatorial band, appears to be a permanent feature 

 which it will be well to observe assiduously. They further 

 urge that careful attention should be paid at the end 

 of this year to observations of the movements of the red 

 spot, of the bright spots on the southern edge of south 

 temperate band announced by Mr. Denning, and of the 

 dark region situated in the south tropical zone. 



The Electric Charge of the Sun. — In No. i, vol. x., 

 of Terrestrial Magnetism and Atmospheric Electricity is re- 

 printed the address " On the Electric Charge of the Sun " 

 delivered bv Prof. Svante Arrhenius before the International 

 Electrical Congress held at St. Louis last Septeinber. 



After briefly discussing the various theories regarding 

 the nature of the sun's repulsive action, the author shows 

 that the theory which e.xplains the phenomena, by pre- 

 mising that the repulsion is due to radiation pressure 

 acting on negatively charged particles, is in accordance with 

 observational records. The particles having a specific 

 weight of 10 and a radius of 0.08 ,11 are those which are 

 repelled at the greatest speed, and would reach our atmo- 

 sphere in about 45.9 hours, an interval of the same order 

 as that obtained by Ricc6 for the time intervening between 

 the probably correlated soiar and terrestrial phenomena. 

 These particles are negatively charged in accordance with 

 Mr. C. T. R. Wilson's proof that such particles are more 

 easily condensed on negative than on positive ions, the 



NO. 1854, VOL. 72] 



ionisation of the solar atinosphere resulting, as Lenard 

 has shown, from the action of the sun's strong ultra- 

 violet radiation. By a simple calculation Prof. Arrhenius 

 shows that the remaining positive charge is balanced, and 

 the balance maintained, by the attraction of negative 

 electrons emitted by other celestial bodies which are 

 negatively charged and lose their charge under the in- 

 fluence of their ultra-violet rays. All such rays coming 

 within a mean distance of 0.063 light-years of the sun will 

 be attracted thereto, and by this means the supply of 

 negative electrons becomes just proportional to the defect 

 thereof. 



Variability of Minor Planet (15), Eunomia.— CiV<:«?nr 

 No. 94 of the Harvard College Observatory is devoted to 

 an account of Prof. Wendell's observations of the minor 

 planet Eunomia, from which he established a variation of 

 magnitude of about 05. The observations were made with 

 a photometer having achromatic prisms and attached to 

 the 15-inch telescope. As the planet was near its stationary 

 point it was compared with the same star, + 13° 1875 

 (mag. 9.0), from March 15 to April i, and the corrected 

 differences varied from -077 to -i-ii. The formula 

 J.D. 24i692o-ii6-f-o.i267 E. expresses the phase and period 

 of the changes. The period is very similar to that found 

 forininor planet (7), Iris, viz. o.i295d., and in both cases 

 It. is still doubtful as to whether the period requires 

 doubling or not. 



F.AINTNESS of Planetarv Nebul.t:.— Some interesting 

 results of calculations appertaining to the luminosity 0I 

 the surfaces of several planetary nebula;, as compared with 

 the surface luminosity of the sun or the moon, are given 

 in a letter written by Mr. J. E. Gore to the current number 

 of the Observatory, 



Dealing with the nebula H, iv. 37, situated near to the 

 pole of the ecliptic, he finds that the ratio of its surface 

 luminosity is to that of the sun's as i :43I96.7XIo^ The 

 similar ratios for the nebuU-e h 3365, 2 5, and G.C. 7027 

 are 1:245.3x10°, 1:1095.5X10°, and 1:434x10' re- 

 spectively; thus the brightest of them, i.e. h 3365, has a 

 surface luminosity of onlv 1/400 that of the moon. 



THE COWTHORPE OAK. 

 T N the Transactions and Proceedings of the Botanical 

 Society of Edinburgh (vol. xxii., part iii., 1904, p. 396) 

 we notice a very interesting article on the Cowthorpe Oak 

 from the pen of Mr. John Clayton. This venerable tree, 

 which stands near the church of Cowthorpe, a small 

 village near Wetherby, is unique among oaks in that its 

 girth is greater than that of any other known tree of its 

 species. Recorded measurements taken about 1700 show 

 that it had at that time a height of So feet with a girth 

 of 78 feet on the ground. Since then various observers 

 have recorded its dimensions and noted at the same time 

 the gradual process of decay, damage by storm, and other 

 points likely to be of interest. The latest measurements 

 were taken by Mr. Clayton himself, and they show that 

 the height is now reduced to 37 feet including dead wood, 

 while the girth on the ground has diminished to 54 feet 

 3 inches. In 1S93 a crop of acorns was produced, from 

 one of which a seedling was reared, and is now planted 

 near its parent as a memorial. 



The tree stands in a warm, sheltered spot in a field 

 which has a gentle slope to the river, and near enough to 

 get a constant supply of water. The process of decay has 

 been going on for the last 200 years. Between 1703 and 

 1722 much damage was done by various storms; never- 

 theless, new leaves are put forth annually. The acorns 

 produced in 1893 were on long stalks — hence the species 

 is Ouercus pedunculata. .'\s regards the age of this giant 

 opinion seems to difl'er. The trunk, being now hollow, 

 precludes all possibility of ever ascertaining the number 

 of year-rings, and no trustworthy data are available before 

 the year 17012 — hence the author has been compelled to 

 rely upon a comparison with the age of other trees. In 

 a tree the duration of life may be taken as composed of 



