November, 1906.] 



KNOWLEDGE & SCIENTIFIC NEWS. 



587 



At what date may we look for that minimum ? Taking the 

 eleven years' period as our guide, about 1900; but the 

 interval, it must be remembered, varies. . . The new wave 

 seems at least likely to be lower than the last, and more 

 of the order of the two jarevious." 



The new wave has turned out quite a small one, with 

 crest in 1901, the year of sunspot minimum, the cold then 

 showing (as in iSbb) a relative maximum. Judging by the 

 present position, we should at least expect no extreme cold 

 (high number of frost days) in the earlier half of 1907. (1 

 may remark that the total of frost days in September (o 

 May appears to present similar relations, though perhaps 

 less definite.) 



I am, yours, &c., 



ALEX. n. MacDOWALL. 



To THE Editors ok " Knowlkdge & Scientific News." 



Sirs, — I notice that you occasionally are good enough to 

 answer queries from correspondents in your valuable 

 monthly, which I have taken in for the last eighteen 

 months, and I should be much obliged if you would explain 

 the cause of the following phenomena. 



Being very much interested in chemistry, and recently 

 having had occasion to burn a small piece of phosphorus 

 under a bell-jar for the purpose of seeing how much light 

 was absorbed by the fumes, I held up the jar (with the plate 

 at the bottom) to the light (incandescent gas). The mantle 

 was visible through the fumes, and looked a milky blue 

 colour, as one might e.xpect. This was done when the 

 fumes were densest. 



When the fumes had subsided considerably I again held 

 the jar to the light. I was surprised to see the fumes faintly 

 (but distinctly) coloured in layers. The colour at the top 

 was orange, then a thin layer of violet, then green, and 

 lastly blue. Each layer blended imperceptibly with the next, 

 like a spectrum, only apparently not quite in the same order. 

 The best position for seeing the colours was when the jar 

 was not quite between the eye and the light, but rather 

 lower. When tipped to one side the colours kept the original 

 horizontal level. When agitated the colours formed wavy 

 lines, but soon regained the original level. .As the fumes 

 subsided more the orange colour gradually displaced the 

 other colours until all the jar was diffused with an even 

 orange colour. The jar used was 6i ins. by 52 ins., and the 

 piece of phosphorus about the size of half a pea. The phos- 

 phorus was ignited by a hot wire, so that no other fumes 

 were mixed with them. The colouring was not seen except 

 between the eye and the light. 



Apologising for troubling you, 



1 irm.iin, Yours Xc, 



P. 11. 

 The Library, TUickhurst Hill. 



[The colours are diffraction fringes formed in the same 

 way as the colours often seen rounti the moon — the corona — 

 when seen through a thin cloud. The blue fringe will be 

 found to completely surround the flame, the tint gradually 

 changing to orange outwards. The outer fringes are in- 

 complete, due to the small size of vessel, and hence .appear 

 as bands.—A.W.P.] 



** Pendulums Used in Gravitation 

 Research." 



To THE Editors of " Knowledge & Scientific News." 



Sirs, — Kindly permit me to correct three errors which have 

 occurred in reproduction of my diagrams on page 561 in 

 your last issue, as they are liable to cause misapprehension. 



ist. The dotted lines suggesting the changes of oscillation 

 plane which distinguish ihe Fouc.uill pendulum are omitted 

 from Fig. 2. 



2nd. The curious " smudge " upon ihi" pendulum rod in 

 Fig. 4 is not an intended portion of the diagram itself. 



3rd. The ring in Fig. 7 to which the wire was hooked, 

 and which was the distinctive feature of that pi'iidulum, is 

 omitted. 



Yours truly, 



Manor Park, W. 11. SHARP. 



October, 1906. 



A Peculiar Optical Effect. 



To the Editors of " Knowledge & Scientific News." 

 .Sirs, — I have frequently noticed a peculiar effect where a 

 number of straight lines run in close proximity, which I 

 am unable to account for. I refer to the fact that (to most 

 eyes at all events) horizontal lines are more easily dis- 

 tinguishable than vertical lines. This is shown in the 

 diagram I send herewith. One would be inclined, on first 

 looking at it, to think that the horizontal lines were further 

 ;ipart than the vertical ones, j'et on turning the whole paper 

 round to a riijht angle, those lines which were vertical be- 

 come horizontal, and are then much clearer than the others. 



ml 



The eflect may be even more noticeable if looked at from 

 some distance. But now another curious result comes in. 

 To my eyes, when the paper is held at a distance (say six 

 feet), the horizontal lines are distinctly the clearer, but if I 

 use strongish glasses, even though the lines be slightly out 

 of focus, the vertical ones are undoubtedly the more dis- 

 tinguishable. 



Ihis effect has its practical value, for draughtsmen will 

 find it better, when using a fine scale, to place it so that the 

 lines run horizontally, turning the paper round if necessary. 



Perhaps some of jour readers can explain the cause of 

 this. 



Yours faithfully, 



B. 



Answeis to Correspondents. 



A. Haiidcl Smith. — The most complete tables of physical 

 and chemical data are to be found in Landolt-Biirnstein, 

 Physikalisch-Chcmische Taliellen (Williams and Xorgate, 

 London). The Chemist's Pocket Book (E. and F. N. Spon) 

 also contains numerous tables. It is impossible to advise 

 further without knowing the particular tables required. 



HaUey's Comet. — Various dates have been put forward for 

 the return of this interesting comet, but the data are not 

 rigid, and consequently the predicted positions and times 

 of perihelion are given with some variance by different 

 authorities. The first predictions were for 19H, then 1912, 

 but the most recent is th.U for 1910, May 24. .May 16 of 

 the same year has also been mentioned. 



Artificial Respiration. 



The newest method is that of Dr. Eisenmenger, of 

 Hungary, who proposes lo restore respiration by 

 acting only on the abdomen, without causing any movement 

 of the thorax. To this end he has devised an apparatus that 

 enables him to increase or diminish at will the atmospheric 

 pressure on the abdomen by a species of suction. A sort of 

 cuirass, fitted with straps and a pad, is tightly fitted over 

 the abdomen ami lower thorax in such a way as to leave an 

 empty space beneath the cuirass and the fleshy parts of the 

 stomach aiul abtlomen. The air in this hollow can be com- 

 pressed or exhausted by means of a pneumatic tube and 

 bellows, and thus the movable envelope of the abdomen can 

 be alternately raised and depressed. Thus the rhythmic 

 movement is transmitted across the .soft internal organs to 

 the diaphragm, which it moves in a corresponding way, thus 

 causing inspiration and expiration. The heart is also 

 affected, and thus gently massaged, and its movement 

 stimulated. 



