248 



NA TURIi 



[July 16, 18c 6 



College is too often bound down by the exigencies of examina- 

 tions to the delivery of certain set lecture courses, and these, 

 together with his own researches and the performance of the 

 many administrative duties that fall to his lot, occupy almost the 

 whole of his time. Let him possess the master-mind of a 

 Hofniann, his hurried visits to his laboratory afford comparatively 

 slight opportunity for the exercise of its full effect on the student. 

 The demonstrator, on the contrary, bears the brunt of the difficult 

 and harassing tutorial work in his close contact with the student 

 in the laboratory, and upon the demonstrator's ability and manner 

 of teaching will depend, in great measure, the student's future 

 style of work. Kor this a grateful University College gives him 

 rather less than it pays to its janitor, and much less than half 

 the amount received by its travelling dairy- maid ! 



I am afraid that the cause of this very real injustice will be 

 found, in part, in the influence of our older universitie.s, where 

 until recently lectures were everything and practical work was 

 naught. Members of these universities on college councils 

 still seem to cling to the old idea, and the majority of the remain- 

 ing members, probably excellent men of business or affairs, have 

 somewhat hazy notions of scientific educational work ; the 

 Professors, who alone of the teaching staff obtain representation 

 on the governing body, are, after all, but human, and can scarcely 

 be expected to labour to disabuse them. 



I fear that, as a body, demonstrators and lecturers are scarcely 

 influential enough to approach the Chancellor of the Exchequer 

 with a view to his impo.singsuch conditions that the renewal of the 

 Treasury grant shall be made to depend upon the redress of their 

 wrongs ; still the injustice of their treatment is undeniable, and 

 perhaps some of your readers can suggest a remedy, 



S.A\II.LE SlIAW. 



A Solar Halo. 



Shortly after 7 o'clock in the evening of July 2, a solar halo 

 was observed from Putney Bridge, West London. 



The appearance consisted of portions of the inner halo (22" 

 from the sun) situated just at the same height above the horizon 

 as the sun. The halo was of a distinct red on the inside of the 

 circle, followed by yellow and by a faintly bluish white light on 

 the outside. There was also a faint parhelion on the right side, 

 .1st outside of the halo. 



Above the sun, at a point where the vertical through the sun 

 ■would have cut the circular halo, there was, instead of the latter, 

 an inverted arch of somewhat hyperbolic shape, the arms of the 

 hyperbola extending upwards and enclosing an angle greater 

 than a right angle. The faint prismatic colours of this arch 

 were placed so that the red was nearest to the sun, and the apex 

 of the inverted arch must have been 22° distant from the sun. 

 The height of the sun above the horizon was estimated to be 

 about 14^ and the phenomenon lasted ten minutes after it had 

 been first observed. The sky was somewhat cloudy. 



West Kensington. H. W.\RTH. 



An Optical Illusion. 



While doing some photographic work with a light from a 

 Welsbach burner, which shone through a small ground glass 

 window in a dark-room, I noticed that when a lamp emitting 

 red rays from its vertical sides was placed in a position so that 

 its top was illuminated by the white light from the window, 

 and while in this light it was then moved by hand to and fro in 

 a horizontal plane, the top appeared to be loose, or displaced in 

 opposite directions to the red sides. The top was of bright tin 

 and its surface sufficiently irregular to cast slight shadows, which 

 rendered the effect very marked. 



This illusion is no doubt due to a physiological action at the 

 retina, in which the impression produced by the white or grey 

 light persists longer than that from the red, causing an apparent 

 lag of the top. The persistency may be still further accounted 

 for when the fact is borne in mind that the lag could only be 

 obtained with weak lights in a dark-room, and therefore with 

 the pupil of the eye largely expanded, and in consequence a 

 relative increase of intensity of the white over the red light 

 upon retinal areas of different sensibility. 



Lamplight or daylight can be used instead of a Welsbach. I 

 found it convenient to vary the intensity and colour of the 

 lights by superposing sheets of coloured tissue-papers. 



New Rochelle, N.V. F. II. Lori.ni;. 



NO. 1394, VOL. 54] 



Food of Chameleons. 



I DO not know whether you care to insert a modest natural 

 history communication, for I apprehend but few of your readers 

 are country naturalists. If you do, it is to this effect. 



It is not easy to keep chameleons alive long in this country, 

 owing to the difficulty of procuring their proper diet. 



I am keeping a Madagascar one, and he thrives very well. 

 The food he seems to prefer to all other is the common green 

 fly with a metallic lustre ; these he takes at once in preference 

 to the finest bluebottles, and when he protrudes his curious long 

 tongue, armed with some glutinous matter, the direction is 

 unerring, and woe to the fly. The chameleonic colour changes 

 are most interesting. K. L. J. KmsnALE. 



Rottingdean. 



Rbntgen Rays. 



Ma.w tubes for Riintgen ray researches have the edge of the 

 kathode mirror opposite the short neck, and in such cases the 

 expedient described by Mr. I'orter in your issue of the l8th 

 ultimo, can very easily be carried out by fitting an india-rubber 

 ring on this neck, winding two coils of copper wire round it, 

 and leaving two or three inches free at one end, which is then 

 bent so as to bring the point sufficiently near to the kathode 

 loop. 



An application of the Riintgen rays has been made in the 

 small local museum here, which promises to make it more 

 generally attractive and useful. Skiagrams of suitable specimens 

 have been taken, and prints from these placed alongside the 

 specimens, so that their external form and the bony structure 

 which supports it may be compared at a glance. 



Keith, X.B. , July 3. Alex. Thurdurn. 



A Curious Connection. 



If new, perhaps the following fact, observed by me, may be 

 worth publishing. In my kitchen I have a mantle on the gas- 

 burner. At present the mantle is in a dilapidated state, and the 

 light defective. I find, however, that, when the water-tap over 

 the kitchen sink is running, the light greatly increases in 

 brilliancy, maintaining that brilliancy as long as the water is 

 running. Margaret McEvoy. 



THE INTERNATIONAL CATALOGUE 

 CONFERENCE. 

 'T*HE International Conference organised by the Royal 

 ■'■ .Society to consider the preparation and publication 

 of an International Catalogue of Scientific Literature was 

 opened in the apartments of the Society at Burlington 

 House on Tuesday. Upon the importance of such a 

 catalogue it is unnecessary to conmient here. The 

 Royal Society has steadily attacked the problem of re- 

 cording and indexing scientific literature, since the middle 

 of this century, when the great author-index was com- 

 menced. More than thirty years ago the Council of the 

 Society resolved that the catalogue according to authors 

 should be followed by an index according to subjects, 

 and a start was made in 1S93. But, as Lord Kelvin 

 pointed out in his last anniversary address, "the con- 

 tinuation of such a work was almost beyond the resources 

 of the Royal Society, and therefore about two years ago 

 a Committee was appointed to take into considera- 

 tion a suggestion that the preparation of com- 

 plete indexes should be effected by international co- 

 operation." The conference now being held is 

 the outcome of this conclusion. Only by securing 

 international co-operation could such a work as that 

 contemplated by the Royal Society be satisfactorily 

 carried out. It is therefore a matter of extreme con- 

 gratulation that the proposal has been so w-armly sup- 

 ported by Governments and Scientific Societies in all 

 parts of the world, as shown by the distinguished men 

 who have been delegated to take part in the conference. 

 The enterprise is one in which all men of science are 

 interested, but of the magnitude of which it is only 

 possible to have a faint conception. To develop a com- 

 prehensive and practicable scheme will be a difficult 

 task, but with a conference constituted like that now 



