July 15, 1922] 



NA TURE 



81 



South Kensington was not only closely associated 

 with the earl)' history of general scientific education, 

 but it recapitulates that history. A permanent 

 memorial there to the technical education movement 

 of the 'seventies and 'eighties is the City and Guilds 

 of London Institute for the Advancement of Technical 

 Education. The Institute was formed in 1878 by the 

 Livery Companies of the City of London, one of its 

 principal objects being the establishment of the 

 Central Technical College to supply higher technical 

 education to productive industry. It was designed 

 originally as the coping-stone of a system of technical 

 schools, and particularly for the training of technical 

 teachers. The foundation-stone of the College was 

 laid by the Prince of Wales in 1881, and the building 

 was completed three years later. Its work is now 

 confined to engineering education, and it is one of the 

 largest and best-equipped schools for this subject in 

 the country. 



The next important movement, which had for its 

 object the development of teaching and research in 

 applied science, culminated in 1907 in the establish- 

 ment of the Imperial College of Science and Technology, 

 to which a Royal Charter was granted. The Board 

 of Education transferred to the new governing body 

 of the Imperial College the control of the Royal College 

 of Science and the Royal School of Mines ; and the 

 Central Technical College, renamed the City and 

 Guilds (Engineering) College, was also brought into 

 the scheme of common administration. Remarkable 

 progress has since been made in developing the re- 

 sources of the colleges for teaching and research. A 

 new building has been erected for the Royal School 



of Mines, and an extension (provided by the Gold- 

 smiths' Company) of the City and Guilds College 

 and others for botany, plant physiology and patho- 

 logy, and chemical technology, while the social 

 needs of the students have been met by the pro- 

 vision of a special building for the Imperial College 

 Union. 



The foregoing list by no means exhausts the buildings 

 at South Kensington. The Natural History Museum 

 (a branch of the British Museum) is in grey terra-cotta, 

 built to the designs of Alfred Waterhouse, and was 

 finished in 1880. It is both a museum and a centre 

 for natural history study and research. The Royal 

 College of Music, a less austere enterprise, was built 

 by Sir Arthur Blomfield and opened in 1894 ; and the 

 Royal School of Art Needlework and the headquarters 

 of the Royal Geographical Society in Kensington 

 Gore must also be mentioned. 



Some final reflections. First and most obvious, 

 the available space at South Kensington is now practi- 

 cally exhausted. Almost the only science which has 

 not been practised at South Kensington is town 

 planning, and there can be no doubt that the area 

 might have been planned more economically. Much 

 still remains to be done in providing new departments 

 of pure and applied science. Under no possible re- 

 organisation of higher education in the metropolis 

 can South Kensington cease to be a most important 

 centre for education and research in science and art. 

 It has great resources in traditions, in men, in materials ; 

 and if, like Oxford, it is already the home of some lost 

 causes, it has a marvellous power of adapting itself 

 to new conditions. 



Dark Nebulae. 1 



By Prof. H. N. Russell, Mount Wilson Observatory. 



IT is now generally believed that many of the dark 

 markings in the Milky Way, and dark starless 

 regions in the sky, are produced by the interposition 

 of huge obscuring clouds between us and the more 

 remote stars. A long list of such dark markings has 

 been given by Barnard, 2 who has done more than anyone 

 else to point out their importance and probable nature. 

 In some cases, as in the Pleiades, Orion, and Ophiuchus, 

 these " regions of obscuration " merge into faintly 

 luminous nebulosity in the vicinity of certain stars, in 

 such a way that there can be no doubt that they lie 

 near these stars in space. 



It thus appears that the obscuring masses or dark 

 nebulas in Ophiuchus and Scorpius are at a distance 

 of 100 to 150 parsecs, those in Taurus at probably 

 about the same distance, and those in Orion some 200 

 parsecs from us, while the dimensions of the individual 

 clouds are themselves measured in parsecs. 



The occurrence of these three great regions of 

 obscuration within a distance which is so small com- 

 pared with that of the galactic clouds indicates that 

 such objects are probably of great cosmical temperature. 



These dark nebulfe usually appear to be quite opaque. 

 In some cases the stars can be seen faintly through 



1 Communication to the National Academy of Sciences, Washington, on 

 March 14. Reprinted from the Proceedings of the Academy, vol. 8, No. 5, 

 May 1922. 



2 Barnard, E. E-, Astrophys. Joum., Chicago, 49, 1919 (1-23). 



NO. 275O, VOL. I IO] 



them, apparently without much change in colour ; 

 but in some examples 3 stars imbedded in dense 

 luminous nebulosity are abnormally red. 



Of the various forms in which matter may be dis- 

 tributed in space, by far the most efficient in producing 

 obscuration is fine dust, since this has the greatest 

 superficial area per unit of mass. In a cloud composed 

 of spherical particles of radius r and density p, dis- 

 tributed at random so that the average quantity of 

 matter per unit volume is d, the extinction of a beam 

 of light in passing through this cloud will be e stellar 

 magnitudes per unit of distance, where e = 0-814 qdjpr. 

 The numerical factor is independent of the physical 

 units which are employed. The factor q is introduced 

 to take account of the complications which occur when 

 the size of the particle becomes comparable with the 

 wave-lengths of light. 4 For particles more than two 

 or three wave-lengths in diameter q is sensibly equal 

 to unity. For smaller particles it increases and is a 

 maximum, 2-56, when the circumference of the particle 

 is 1 -12 times the wave-length. It then rapidly 

 diminishes and becomes nearly equal to 14/3 x (2?rr/A) 

 for particles of less than half this diameter. 5 The ratio 



3 Seares, F. H., and Hubble, E. P., ibid., 52, 1920 (8-22); .1//. Wilson 

 Contr., No. 1S7. 



4 Schwarzschild, K., " Sitzungsberichte der K. B. Akad. der Wiss.," 

 Math.-Phvs. KL, Munchen, 31, 1901 (293-33S) ; Proudman, Monthly Not., 

 R.A.S., London, 73, 1913 (535-539)- 



5 Barnard, E. E., Astrophys. Joum., Chicago, 38, 1913 (496-501). 



