Dec. 26, 1889] 



NATURE 



183 



grass called lalang {Imperata cylindrica, Cyr. ), which is not 

 only useless, but very injurious, both by reason of its inflamma- 

 bility, and because it prevents any cultivation of the land covered 

 by it, except with a great deal of labour and expense. Wherever 

 the land is burnt or having been under cultivation is suffered to 

 run to waste, it is soon covered with lalang, whatever may have 

 been the previous vegetation, except where the soil is sandy, or 

 wet, or shaded by trees. The treatment of the soil by chemicals, 

 such as salt, sulphate of iron, &c., apart from the heavy expense 

 connected with it, is liable to have a very injurious efTect, even 

 for many years, on the plants with which the ground is after- 

 wards afforested. The introduction of some more actively 

 growing plant to combat and destroy the lalang, has been pro- 

 posed, but this would be to destroy one noxious weed by another 

 still more noxious. When trees are tall enough to throw a 

 shade upon the ground, the lalang quickly disappears, nor can 

 it penetrate even into forest glades if but a few trees bar its 

 progress. It is suggested, therefore, that shade trees and 

 bushes should be gradually planted. 



OUR ASTRONOMICAL COLUMN. 



Objects for the Spectroscope. 



Sidereal Time at Greenwich at 10 p.m., December 26 = 4h. 

 22m. 20s. 



Remarks. 



(i) This is described in the General Catalogue as an exceed- 

 ingly interesting object, but very faint and small; according to 

 Hind it is variable. I have not been able to find any record 

 of its spectrum. Continuous observations over a considerable 

 period, even with small dispersion, may throw light upon the 

 nature of the changes which take place. 



(2) A star of Group II., in which Duner records the bands 

 2-8. Bands 2 and 3 are the strongest, indicating that the star 

 is well advanced in condensation towards Group III. As in 

 similar stars, dark metallic lines and lines of hydrogen should 

 receive special attention, as the stages at which these make their 

 appearance have not yet been determined. 



(3) Vogel classes this with stars of the solar type, and the 

 usual differential observations are suggested. (For criteria, see 

 p. 20.) 



(4) According to Konkoly, this is a star of Group IV. The 

 usual observations of the relative intensities of the hydrogen and 

 metallic lines are required, so that the star maybe placed in line 

 with others on the temperature curve. 



(5) This is a variable star of Group VI., but the range of 

 variation is small (6-5-8*5). The origin of variability in stars of 

 this group has not yet been satisfactorily explained, and there is 

 no record of the spectroscopic changes which accompany the 

 changes in magnitude. Further observations are therefore neces- 

 sary, and it is suggested that variations in the intensities of the 

 carbon flutings should be particularly noted. The star was at 

 minimum on October 23. 



(6) This variable reached its maximum on December 21, and, 

 as the period is only 86 days, observations may be made from 

 maximum to minimum, providing that sufficient optical power is 

 employed. The magnitude ranges from about 9 at maximum to 

 14 at minimum. The colour is stated to vary from white at 

 maximum to reddish at minimum. The spectrum has been 

 described as continuous (probably near maximum), but the 

 colour-changes indicate that considerable variations in the 

 spectrum may also be expected. 



(7) The spectrum of Neptune was first observed by Secchi, 

 in 1869. He noted that there were three broad dark bands, 

 which were nebulous at the edges, and that there was a remark- 

 able absence of red light. Vogel gave a more detailed account 

 of the spectrum in i?>']2 [Bothkamp Beobachlungen, 1872, p. 71). 

 The bands then recorded were as follows ; — 



Wave-lengths. 



597 



5657 



556 



540 



518 



513 



507 



485-8 



477 



Remarks. 

 End of spectrum. 

 End of a wide dark band. 

 Very feeble band. 

 Middle of the darkest band. 

 Faint band. 



Middle of a dark band. 

 Middle of a wide dark band. 



The whole spectrum is very similar to that of Uranus. The 

 proximity of the edges of some of the dark bands to the bright 

 flutings of carbon and manganese led Prof. Lockyer to suggest 

 that in Uranus and Neptune we might have to deal with the 

 radiation of those substances, the dark bands being produced 

 by contrast. Acting on this suggestion, I made observations of 

 Uranus with a lo-inch equatorial, and afterwards, in conjunc- 

 tion with Mr. Taylor, with Mr. Common's 5-foot reflector. 

 Direct comparisons certainly showed coincidences of the flutings 

 of carbon with luminous parts of the spectrum. No solar lines 

 were visible, but Dr. Huggins has recently photographed the 

 spectrum, and found nothing but solar lines. In a recent obser- 

 vation of Neptune, I thought the bright flutings were more 

 evident than in Uranus, but I have not had an opportunity of 

 making comparisons. Further observations with reference to 

 the existence of bright flutings are suggested. A. Fowler. 



Variable Star in Cluster G.C. 3636. — Prof. Pickering 

 writes (Astr. JSachr., 2941) that photographs are being taken 

 at Wilson's Peak, Southern California, with a telescope of 13 

 inches aperture. Four photographs, with exposures of about 

 one hour each, were taken of the above cluster, whose position 

 for 1900 is R.A. I3h. 37m. 35s., Decl. + 28° 52'-9. A star 

 about twenty seconds south of the centre of the cluster was 

 found to be much brighter on May 21 and June 8, 1889, than 

 on May 31 and June 17, 1889. Two maxima seem to be indi- 

 cated by the photographs separated by an interval, during which 

 the star becomes comparatively faint. Visual observations made 

 at Cambridge Observatory since June appear to confirm this 

 variability. 



Changes in Lunar Craters. — A few observations made 

 by Prof. Thury {A sir. Nachr., 2940), of craters in the terraced 

 ring of Plinius, indicate some striking changes. On November I, 

 Plinius presented the same aspect as that described in 1882 by 

 MM. Elger, Gaudibert, and H. Klein. Two craters, cutting 

 one another, appear in the middle of the ring, and it is thought 

 that one of these was not visible in the middle of September. 

 The central opening seems to have been enlarged, for on Nov- 

 ember I its diameter was estimated as at least one-third of the 

 total crater, whereas in September the diameter of the opening 

 was rather less than one-fourth of the total diameter. 



The interpretation put by Prof. Thury upon these appearances 

 is that in the centre of Plinius there are two small craters, the 

 aspect of which is modified by the different amounts of snow 

 and ice about them. Emissions of heated gas and vapour would 

 affect considerably the state of the lunar surface, for if, in the 

 beginning of an eruption, water-vapour were predominant, it 

 would be immediately condensed around the crater, forming a 

 circular field of snow, so that the apparent enlargement of the 

 opening may be due to the melting of the snow surrounding it 

 by the hot gases emitted. 



ON THE FUTURE OF OUR TECHNICAL 

 EDUCATION. 



T AST week we referred to an address delivered by Sir Henry 

 -'-' Roscoe at Goldsmiths' Hall on Tuesday, December 17, 

 after the distribution of the prizes and certificates to the students of 

 the City and Guilds of London Institute. He spoke as follows : — 

 In his admirable address delivered last year on a similar 

 occasion to the present, Sir Lyon Playfair pointed out that 

 one of the important objects for which the City Guilds were 

 originally founded was to develop and restore arts and sciences, 



