February ly, igioj 



NA TURE 



471 



bodies surrounding the sun ; this theory is supported by 

 the observation that a fair percentage of the Hght is 

 polarised. The recent observation of Prof. Fowler 

 (Nature, vol. Ixxxi., p. 396, September 30, igog), who, 

 during an auroral display, was able to detect the aurora 

 line everywhere, " even in the light reflected by a pocket- 

 handerchief, " illustrates the danger of attributing the 

 auroral radiation to the spectrum of the Light, simply 

 because it is seen contemporaneously. 



To decide the question of the spectrum of the Light, 

 photographic observations, if possible, were desirable, and, 

 in 1883, Mr. Michie Smith attempted the task of photo- 

 graphing it, but was unsuccessful. Now, however. Dr. 

 Fath has succeeded in obtaining a photograph after 

 exercising a great deal of care and ingenuity in overcoming 

 the numerous difficulties. 



The first attempts were made, at the instigation of Prof. 

 Campbell, in 1907 at Mount Hamilton. The spec;rograph 

 was especially designed and constructed for this research, 

 and has an aperture of jr mm. ; the focal length of the 

 collimator is 814 mm., and that of the camera is 154 mm. 

 Rigidity, to withstand flexure or distortion over long 

 periods, is the main feature of the frame, which is made 

 of well-seasoned pine 13 mm. thick, shellaced inside and 

 out, and put together with glue and screws. The prism 

 is of light flint having a refractive index of i-6ii for 

 H7, and was set for the minimum deviation of this ray ; 

 the resulting spectrum is about 2-2 mm. in length from 

 A 5000 to \ 3900. 



In the autumn, when the Zodiacal Light appears in the 

 morning above the eastern horizon, less than one hour 

 before sunrise is available for the exposures, which there- 

 fore have to be accumulative. As the altitude of the Lick 

 Observatory is 1283 metres, it was expected that dawn 

 might commence before the zenith distance of the sun was 

 ioS°, the usually accepted value, and in the first experi- 

 ments the exposure was always stopped when the computed 

 zenith distance was 111°; later experiments showed this 

 precaution to be unnecessary. 



In .August, 1907, an exposure was made, over the period 

 .\ugust 8 to 15, totalling 6h. im., and in the very faint 

 spectrum secured absorption lines at \ 4300 and X 3950 

 were suspected. 



A stronger spectrum was obtained in October, 1907, with 

 a total exposure of iih, gm., but still the traces of absorp- 

 tion were too faint to permit of any definite conclusions. 

 .\nother attempt in the autumn of 1908 only served to 

 illustrate the numerous pitfalls awaiting the observer of 

 this evanescent spectrum. Jupiter and Venus were above 

 the horizon, reflecting sunlight, and this so complicated 

 matters that the experiments had to be abandoned. 



On his translation to Mount Wilson. Dr. Fath resumed 

 the inquiry, and, by the courtesy of Prof. Campbell, was 

 able to use the same instrument. Elaborate precautions 

 were taken to eliminate any chance of " shift " caused 

 by the vibration or change of temperature of the spectro- 

 graph ; the instrument was also mounted on an azimuth 

 slide, so that it could be moved in azimuth some 1;°, in 

 order to follow the brightest part of the Zodiacal Light. 

 The width of the slit employed was 0-41 mm., and at this 

 width the solar lines H and K are not separated in the 

 spectrum. The exposures extendid from 1909 September 12 

 to September 25 under very favourable conditions, and 

 were always arrested a minute or two before the time 

 calculated for the zenith distance of the sun to be loS". 

 Careful watch was kept for any abnormal dawn or other 

 phenomena which might vitiate the results, but none was 

 observed. 



With a total exposure of lah. 31m., on a Lumiire 

 " Sigma " plate, a spectrum was obtained, under these 

 conditions, which, so far as its small size will allow one 

 to judge, resembles the solar spectrum exactly. Two 

 absorption lines are certainly seen, and a compnrison soec- 

 trum of daylight shows these to be G and a blend of H 

 and K in the solar soectrum. There are no signs of bright 

 lines on anv one of the spectra obtainW, and therefore, 

 as Dr. Fath concludes, we seem justified, so far as such 

 small, impure spectra can tend justification, in concluding 

 that the Zodiacal Light is nothing more than reflected 

 sunlight. 



NO. 2103, VOL. 82] 



To support this conclusion it is, of course, desirable that 

 the woik should be continued, using a naiTOW sUt to> 

 obtain greater purity of spectrum ; but this entails the 

 employment of much quicker plates than are at present 

 available, or a much longer exposure. The latter is at 

 present probably the most feasible plan, but when one 

 remembers that the hours of exposure must be moonless, 

 planetless, and clear, it is obvious that several months 

 would be necessary to complete one such exposure. This 

 means that special precautions to secure the constancy of 

 the spectrograph would be necessary, and Dr. Fath 

 suggests the construction of one with a metal frame, which 

 would be less likely to suffer change than a wooden one, 

 and could be maintained at a fairly constant temperature. 



W. E. ROLSTON. 



TECHNICAL EDUCATION IN GERMANY AND 

 THE UNITED KINGDOM. 



A T the request of Mr. R. Blair, the executive officer 

 ■^ of the London County Council Education Committee,, 

 a valuable memorandum has been drawn up by Dr. F. 

 Rose on the qualifications of the students trained at the 

 German technical high schools in comparison with those 

 of students at British universities and technical institutions 

 of university rank. This memorandum, with the tabulal 

 portion abridged, is subjoined, and it contains facts of 

 great interest and importance. Referring to it, Mr. Blair 

 says : — 



"The memorandum shows that one or two broad state- 

 ments of fact may be made, and these deserve, if they do 

 not demand, attention. First, the schools of the United' 

 Kingdom do an immense amount of valuable work in the 

 evening — my own view is that the work is unparalleled. 

 So much further education in the evening is partly due to 

 the fact that a life of earning and independence begins 

 earlier in the United Kingdom than in Germany, and is 

 partly an indication of the inadequacy of the day work in- 

 these islands. It is hardly possible — and I have not 

 attempted to do it — to assess this evening work in such a 

 way as to place it side by side with the day work in the 

 United Kingdom in comparing the latter with German 

 day work, and such a comparison would also have required' 

 an appreciation of the evening work in Germany. But it 

 has much value. Secondly, taking, as far as one can, com- 

 parable institutions, there are 12,000 fully qualified students 

 attending day institutions for the highest technical train- 

 ing in Germany, and only about 3600 in the LTnited 

 Kingdom. The German courses are, speaking generally, 

 longer and the previous preparation better. Further, this 

 great difference in quality and quantity of the work done 

 has existed for more than a generation ; and these highly 

 qualified German students have found, and do find, their 

 way into agriculture and industry, because the German 

 people believe in the application of trained intelligence to 

 all forms of national activity." 



Dr. Rose's report, in an abridged form, is reprinted' 

 below. 



Although there is little doubt that the majority of 

 students trained in German technical universities actually 

 take up industrial positions upon leaving, it is impossible 

 to give any detailed information, as no statistics on the 

 subject have been published or are obtainable. Nine 

 years ago I carried out an investigation to show to what 

 an extent the German chemical industries had benefited' 

 from the chemical instruction available at universities and 

 technical universities. The proportions still hold good for 

 the present day, although the figures have increased.^ It 

 was found that there were about 4000 academically trained' 

 chemists in the different branches of the chemical industry. 

 The value of the annual production of the chemical indus- 

 tries was estimated at ^0,000,000!. 



The total number of chemists trained in Germany was 

 estimated at the same time at about 7000. It would not 

 be going too far to say that at least four-fifths of the 

 German students actually take up positions in industries 

 and technical work when thev leave the technical universi- 



