April 21, 1910J 



NATURE 



225 



might become a by-product of an industrial opera- 

 tion. 



.\I. Flammarion suggests that if there is any 

 palpable material at so great a distance from the 

 head, it might be possible to measure the minute rise 

 of temperature produced by the earth rushing through 

 it at the rate of 77 kms. (forty-eight miles) per second. 



Fig. 3. — Halley's Comet, 1910, February 10. Photographed at Ottawa. I 



The possibility of detecting the nucleus of the 

 comet when it is crossing the sun's disc appears to 

 be very remote. As pointed out by Prof. W. H. 

 Pickering, a solid dark mass would need to have a 

 diameter of at least seventy miles in order to be de- 

 tected under these conditions, and, from the fact that 

 Herr .Archenhold saw a twelfth-magnitude star tran- 



FiG. 4.— Halley s Comet, 1910. March 5. From a criwii g by M. Baldet. 



sitted by the comet, on December 5, without chang- 

 ing either in colour or brilliancy, it is extremely 

 unlikely that masses of this order of size are con- 

 tained in the comet's head ; but the Kodaikanal 

 spectroheliograph, in the hands of Mr. Evershed, 

 may be able to disclose the cometary vapours during 

 the transit. 



NO. 21 12, VOL. 83] 



There have been many surmises as to what will be 

 the effect on the earth and atmosphere. Some of these 

 are notable only for their extravagance, but it does 

 seem probable that an exceptional display of aurora 

 may be generated, and also that we may experience 

 the mistiness of the atmosphere which was generally 

 noted in 1861, before it was known that we had 

 passed through the tail of the great comet of that 

 year. It has been suggested, too, that we may see 

 the extension of the tail as a series of diverging 

 streamers, as was also noted in 1861. 



Reports from China state that the comet is being 

 used as an omen to inflame the rioters in the dis- 

 affected districts, and that the authorities are exhibit- 

 ing pictures of the comet, with accounts of its previous 

 apparition without ill-effects, in order to reassure the 

 inhabitants. While there is, of course, no possible 

 likelihood of serious misapprehension in this country, 

 it is obvious that there yet lingers a certain amount of 

 superstition concerning the baneful effects of comets. 

 We would suggest to all teachers that the May appari- 

 tion will afford an excellent opportunity for giving 

 real. " live " nature-study lessons, which should effec- 

 tivelv eradicate such superstitious fancies from the 

 minds of the rising generation. 



ROM AH BRITAIN.' 



THE first of the two volumes referred to below 

 contains a fully illustrated account of the ex- 

 cavations carried out early in 1907 by the Manchester 

 and District Branch of the Classical Association on 

 the site of the Roman fort at Castlefield, Manchester. 

 The second volume is a supplementary volume by the 

 same association, describing excavations of an earth- 

 work at Toothill, Cheshire, and at the Roman Fort 

 Melandra. 



The first volume is something more than a mere 

 dry-as-dust description of excavations. It contains a 

 number of very interesting and informing essays 

 dealing with different departments of the subject, and 

 written by experts, so that the general reader will 

 have no difficulty in understanding the nature and 

 value of the work that has been so efficiently carried 

 out. Both volumes are ably edited by Mr. F. A. 

 Bruton, of the Manchester Grammar School. 



An interesting article on, the name of the fort, by 

 Prof. James Tait, shows how difficult it is to suggest 

 an etvmology of an ancient place-name which will 

 withstand the assault of destructive criticism. The 

 name Mancunium, which is usually associated with 

 the Roman fort at Manchester, has been derived by 

 various authorities from the Welsh, main, " a stone " ; 

 from the Welsh man, "a place," and cetiion, '" skins"; 

 from the Welsh meini cochion, " redstones " ; and 

 from the Old Celtic mammion, suggesting a deriva- 

 tion from mamma, "mother." The last derivation 

 applies to the form Mamcunio, one of the half-dozen 

 different readings found in various ancient manu- 

 scripts. 



Among the inscriptions found in the course of the 

 excavations are several on altars dedicating them to 

 the goddess " Fortune, the Preserver." The inscrip- 

 tions, however, give very little information as to the 

 details of the Roman occupation, though one inscrip- 

 tion appears to imply that at one time soldiers from 

 Raetia (Tyrol) and from Noricum formed part of 

 the Manchester garrison. 



Among the objects were a considerable number of 

 coins and articles of bronze, silver, iron, and glass. 



1 "Ihe Roman Fort at Manchester." Edited by F. A. BrotOD. (.Man 

 Chester : University Press ; London : Sherrat: and Hughes, 1909 ) Price 

 5^. net. 



" Excavations at Toothill and Melandra." Edited by F. A. Bnitox 

 (Manchester : University Press ; London : Sherratt and Hughes, 1909.) 



