22 



NATURE 



[November 3, 1910 



by Prof. Lowell in which he showed that particles repelled 

 by light-pressure along the tail of Halley's comet travelled 

 with accelerating velocities. An important addition to 

 these results is now published in No. 48 of the Lowell 

 Observatory Bulletins. By comparing the images shown 

 on direct ' photographs with those shown on contem- 

 |X)raneous objective-prism spectrograms, taken under con- 

 ditions which permit the comparison, Prof. Lowell has 

 educed evidence that the gaseous molecules of the tail 

 were repelled by light-pressure. 



A series of spectrograms, taken during April and May, 

 shows that the constituents of the tail varied consider- 

 ably from one date to another. But the evidence indicates 

 that on May 23 about 70 per cent, of the radiations repre- 

 sented on the spectrograms was due to emission, the re- 

 maining 30 per cent, being taken up by the continuous 

 spectrum. That is to say, that the knots previously 

 measured, on the direct photographs for May 23, were 

 composed chiefly of gaseous molecules. As these knots 

 showed, by their accelerating velocities, the action of a 

 repulsive force exerted from the sun, it follows that light- 

 pressure is competent to repel gaseous molecules. 



Confirmation of this important result is derived from a 

 similar comparative study of the direct and spectral 

 images of the tail of Morehouse's comet. The spectro- 

 scopic evidence in that case indicated that practically all 

 the light recorded on the plates was emitted by gaseous 

 particles, yet the direct photographs afforded evidence of 

 the action of light-pressure. 



The Dark Band surrounding the Polar Caps of 

 Mars. — Readers of these columns will remember the dis- 

 cussion raised by M. Antoniadi's contention that the dark 

 band seen circling the polar cap on Mars is simply a 

 contrast effect. In support of this contention M. 

 Antoniadi stated (see Nature, December 23, 1909, vol. 

 Ixxxii., p. 227) that photographs of the planet, taken in 

 America, did not show the dark band, although at the 

 same time they showed that the cap was not brighter than 

 the continental areas, and therefore irradiation could not 

 be adduced as the reason for the absence of the band. 

 Prof. Lowell, in a note appearing in No. 4448 of the 

 Astronomische Nachrichten, emphatically states that the 

 photographs do show that the polar cap is brighter than 

 the " continents," and actually irradiates in consequence 

 beyond the confines of the disc. Further, the screen 

 through which the photographs were taken was such that 

 the relative brightness of the caps would be considerably 

 modified. 



The Spectrum of Nova Sagittarii No. 2. — The nova 

 recently announced by Mrs. Fleming appears on sixteen 

 photographs taken at Arequipa between March 21 and 

 June 10 ; the magnitude varied from 7-8 to 8-6 between 

 those dates. The spectrum is quite faint, but shows the 

 hydrogen lines, H/3, H7, H5, He, Hf, and Hrj, bright ; a 

 trace of Hy as a dark line is seen on the less refrangible 

 edge of the bright Hy line. 



The star does not appear on seventeen photographs 

 taken between July 23, 1889, and October 7, 1909, 

 although stars down to magnitude 12-0 are shown on the 

 majority of the plates ; one plate shows the fifteenth 

 magnitude or fainter. 



A visual observation by Mr. Leon Campbell, using the 

 Harvard 24-inch reflector on October 3, showed the magni- 

 tude of the nova to be 10-5. 



Prof. Millosevich, on October 15, determined the position, 

 reduced to 19100, as i7h. S4m. 26-28s., —27° 32' 521", 

 and the magnitude as 10-4 (Astronomische Nachrichten, 

 No. 4448). 



A New Variable Star or a Nova, 971910 Cygni. — In 

 No. 4448 of the Astronomische Nachrichten Mr. Hinks 

 records the discovery of what appears to be a new star, 

 or an unrecorded variable, on plates taken by him on 

 August 7, 10, and 12, 1909. The position of the object 

 is R.A. = i9h. 49m. S5-OIS., dec. = 4-36° 46' 57-4* (1900), 

 and the approximate magnitudes on the dates named were 

 104, IO-2, and 10-5 respectively. 



Plates taken on August 17, 19, and 26 show no 

 trace of an object in this position, although those of 

 August 17 and 26 show stars down to magnitude 12-5 ; 

 nor could the star be found visually on September 19 and 



NO. 2140, VOL. 85] 



26, when it should have been visible if brighter thai; 

 mag. 130. 



Mr. Hinks publishes a chart of the region around tb. 

 object, and asks for any available information as to iis 

 appearance on photographs which may have been taken 

 elsewhere. 



New Variable Stars in Harvard Map, No. 52. — In 

 Circular No. 162 of the Harvard College Observatory 

 Prof. Pickering announces the discovery, by Miss Cannon, 

 of twenty-two new variable stars on No. 52 of the Harvard 

 maps. The region of the plate is i8h. —60°, and 

 altogether thirty-five variables were found. Some of the, 

 new variables have ranges of three or four magnitudes, 

 one, D.M. —57° 8613, varying from 76 to 100 ; this is 

 of the Algol type, and has a spectrum of the fifth class. 



ANTHROPOLOGY AT THE BRITISH 

 ASSOCIATION. 

 'T'HE Anthropological Section at the Sheffield meeting was 

 presided over by Mr. W. Crooke, whose works dealing 

 with the ethnology of India are well known and highly 

 valued by all anthropologists. His address has already 

 appeared in Nature (September 29) and need not be alluded 

 to here, except to refer to the tribute that was paid to the 

 work of Dr. Tylor, who has so lately resigned his pro- 

 fessorship at Oxford, and who presided over the department 

 (as it then was) of anthropology at the last Sheffield 

 meeting, held thirty-one years ago. 



A feature of the section's work was the joint discussion 

 with Section L (Education) on the measurement of in- 

 telligence in school children, to which Dr. Spearman, Dr. 

 Lipmann, Dr. Myers, and Messrs. Burt, Brovirn, and Gray | 

 contributed. A report of this discussion will be given in I 

 the account of the proceedings in Section L. 



Beyond this the work of the section ran on the usual 

 lines, the number of archaeological papers being again a 

 prominent feature. The section, as usual, had the advan- ! 

 tage of hearing reports on their work by members of the 

 British Schools of Archaeology at Athens, Rome, and in 

 Egypt, and also from gentlemen who have been excavating 

 and exploring in the British Isles. 



In the following summary the papers are broadly grouped 

 together under the various subjects with which they dealt. 



Archaeology. ^^ 



Mr. T. Ashby described the excavations which have taken 

 place at Caerwent, the site of Venta Silurum. These have 

 consisted of the uncovering of several more houses, and of 

 the excavation of the central insula to the north of the city, 

 which contains the Forum and Basilica. This latter had no 

 apses, and from its S. aisle at each end were entrances into 

 the streets. The Forum was surrounded by an ambulatory 

 and shops. Numerous skeletons were found in another part 

 of the city, but were not contemporary, being obviously of 

 post-Roman date. Closely akin to this paper was Prof. 

 Bosanquet's account of the excavations at Caersws, under- 

 taken by the Liverpool committee for excavation and 

 research in Wales and the Marches. 



Mr. H. D. Acland presented a paper on some prehistoric 

 monuments in the Scilly Isles, which consisted of a 

 description of two groups of menhirs. Several of those of 

 one group have a constant orientation differing 4° from a 

 normal bearing. A group of intersecting banks was also 

 described, which have a similar variation as the menhirs. 



The excavation of a broch at Cogle, VVatten, Caithness, 

 was described by Mr. Alexander Sutherland. The building 

 had been overgrown with vegetation, and five successive 

 layers of ashes and pavement were found. Among the 

 Neolithic remains were several stone pestles, discovered in 

 the lowest stratum ; these were of a basalt-like stone and 

 were originally of oval or oblong shape, but had been worn 

 down by constant pounding until some of them had become 

 circular. The broch was 30 feet in diameter. 



The Rev. Dr. Irving read a paper on the prehistoric 

 horse, found some little time ago at Bishop's Stortford. 

 Careful comparisons have been made with other skeletons, 

 and the conclusion seems warranted that it represents a late 

 Pleistocene race, which has survived into Neolithic, Bronze, 

 or the Early Iron period, the age of the deposit being 



