4i6 



NA TURE 



[August 25, 1904 



most interesting pictures shown by Dr. Cornish at the Royal 

 Geographical Society and elsewhere, and the descriptive 

 notes which have been prepared for the slides direct atten- 

 tion to the chief points of interest. 



We have received from New York the first number of the 

 Mining Magazine, an international monthly review of 

 progress in mining and metallurgy. Though new in name, 

 the magazine is really a development of the Pacific Coast 

 Miner, a weekly journal of repute. It is edited by 

 specialists, and the illustrations and typography reach the 

 high standard that characterises American magazines. 

 The contents are of varied interest. Mr. J. A. Church gives 

 a sketch of mining, past and future. The geographical 

 distribution of ores within the United States is discussed 

 by Mr. F. L. Ransome. Mr. Carl Henrich gives an 

 admirably illustrated account of the Guanajuato mining 

 district of Mexico ; and Mr. Henry S. Fleming discusses the 

 commercial divisions of the competitive coal markets. 

 Lastly, a useful index of current literature is provided. 



OUR ASTRONOMICAL COLUMN. 



Visibility of the Martian Canals. — In Bulletin No. 12 

 of the Lowell Observatory Mr. Lowell extends and sums up 

 the results recently outlined by him in a communication 

 to the American Academy of Sciences under the title " The 

 Cartouches of the Canals of Mars." During the last 

 opposition he made 372 drawings of the planet's visible 

 surface on 143 nights, and by carefully examining these 

 and eliminating all known extrinsic variations he secured 

 sufficient data to enable him to plot a visibility curve for 

 each canal, between January ig and July 26, which he 

 believes exhibits only the actual, intrinsic variability of the 

 marking in question. This curve he calls the " cartouche 

 of that canal. 



Analysing the 109 curves thus obtained he finds, except 

 in three cases, a well marked seasonal variation. These 

 curves are not exactly similar, but on arranging them in 

 a steadily progressive order it was seen that the order was 

 one of latitude, the increase of visibility taking place in 

 the north polar canals first and in the equatorial canals 

 last. The reason assigned for the earlier quickening of 

 the polar canals is that all these markings are due to 

 vegetable growth, which requires both warm sunshine and 

 water for its increase, and, as the general surface of Mars 

 is devoid of water, this growth has to await the arrival 

 of the liberated fluid from the polar caps before it can 

 assume its vernal appearance. Naturally, the sun having 

 alreadv passed the summer solstice, those portions of the 

 planet's surface nearer to the water supply will be the first 

 to grow the new vegetation. 



Further considerations, dealt with in extenso in the 

 Bulletin, lead Mr. Lowell to the conclusion that both the 

 anomalies and the generalities he has discovered argue for 

 the artificial origin of the Martian canals. 



Total Solar Eclipse of 1905. — An article in the August 

 number of the Bulletin de la Soci(!t6 astronotnique de France 

 gives a number of details concerning the eclipse of 1905, 

 and maps showing the entire path and the sections of it 

 which traverse Spain and Tunis. A set of diagrams show- 

 ing the appearance, at various places, of the greatest phase 

 of the eclipse, indicates that for Paris the eclipse commences 

 at i2h. 31m. (Paris Civil M.T.), has its greatest phase 

 (0818) at I3h. ig-im., and finishes at I4h. 31.7m. 



Solar Prominences during 1903. — In No. 6, vol. xxxiii., 

 of the Memorie della Societa degli Spettroscopisti Italiani, 

 Prof. Mascari summarises the results of the observations 

 of prominences made at Catania during 1903. 



\'ery few prominences were seen during the first months 

 of the year, but they were notably augmented later. In 

 January and February the phenomena presented themselves 

 with equal intensity in each hemisphere, but in the second 

 and third trimestres they prevailed in the northern hemi- 

 sphere, whilst in the fourth they were more numerous in 

 southern latitudes. 



The number of days without prominences during 1903 

 was 38 per cent, of the total number of days of observ- 

 ation, instead of 67 per cent, as in 1902. The mean latitude 

 of the prominences in 1903 was 42''i, as compared with 

 48°-4 in the previous vear. The undecennial minimum of 

 prominence activity apparently occurred in October, 1902. 



The Lowell Spectrograph. — In No. i, vol. xx., of the 

 Astrophysical Journal, Mr. V. M. Slipher gives a detailed 

 description of the complete spectrographic equipment 

 obtained for the Lowell Observatory from Mr. J. A. 

 Brashear in -1901. 



The chief instrument differs but little from the Mills 

 spectrograph (Lick), and its linear and angular dispersion 

 at H7, as compared with the other large instruments of 

 its class, may be seen from the following table : — 



Dispel 

 Focal length 



NO. I817, VOL. 70J 



Mr. Slipher.'s communication gives all the details of the 

 instrument's construction and mounting, and is illustrated 

 by several photographs and colour-curves. 



A New Band Spectru.m of Nitrogen. — Whilst photo- 

 graphing the spectrum of the afterglow from metallic spark 

 discharges in an atmosphere of nitrogen, Mr. Percival Lewis, 

 of the University of California, has discovered what is 

 presumably a new band spectrum of nitrogen. He found 

 that the afterglow occurred only in chemically prepared, 

 dried and purified nitrogen, and then only when a strong 

 condenser tiischarge was employed. 



The spectrum is discontinuous, consisting of lines and 

 bands, some of the latter belonging to Deslandre's third 

 group, whilst others were of unknown origin. No after- 

 glow occurred in the metallic vapours unless there was an 

 afterglow in the gas. New bands occur in most of the 

 spectra obtained at \\ 2750, 2890, 3035, and 3200, whilst 

 others, at approximate wave-lengths 3380, 3575, 3805, 4130, 

 and 4540, only occur in some of the photographs. Of the 

 latter bands several may be due to NO, but none of them 

 are found in the spectrum of NO, {Astrophysical Journal, 

 No. I, vol. .XX.). 



THE PERSEID METEORIC SHOWER OF 1904. 



T^HIS shower has not furnished a rich display this year; 

 in fact, the number of meteors visible appears to have 

 been decidedly below the average. Yet there was no moon- 

 light to offer any impediment, and the nights were very 

 clear just at the important time. 



On August 9 there were a few Perseids, but the meteors 

 recorded from all sources little exceeded the average number 

 observable on an ordinary night in August, and I wrote 

 down in my notebook that I had never seen so few meteors 

 on August Q in any previous year. 



On August 10 there was an increase in the number visible, 

 but I made no lengthy observations. 



On August II, between loh. 30m. and I3h. 30m., Perseids 

 were falling at the rate of about 25 per hour for one 

 observer, and the radiant was at 46°-)- 58° from 37 paths. 

 This horary rate is for an observer who registered a few 

 of the tracks, and whose attention, therefore, w'as not given 

 continuously to the sky. Mr. McHarg at Lisburn, Ireland, 

 savs that from loh. to iih. local time the Perseids averaged 

 30 to the hour. Mr. J. Webb, of Bristol, counted 21 between 

 gh. 50m. and loh. 50m. ; Mr. W. E. Besley, of London, 

 saw 66 meteors in 3 hours between loh. 30m. and i3h. 30m., 

 and others must have been missed while records were being 

 made. He saw meteors as bright as Jupiter or \'enus at 

 loh. 301T1., iih. 14m., iih. 2om., and I3h. 7m. Mr. 

 McHarg noted a brilliant green fireball > 9 at loh. 20m. 

 G.M.T. falling in Libra a little west of a and directed 

 from 6 Bocitis, so it was probably a Perseid. 



