496 



NATURE 



[September 22, 



frequency of the two enantiomorphs. We might even predict 

 that if a chemist were to spend his life in the preparation of 

 innumerable and smallest physically sensible amounts of a 

 normally racemoid substance, he would with fine enough 

 apparatus ultimately be able to detect some amount of rotatory 

 polarisation. In nature, where during countless ages (and in 

 the past probably much more actively than at present) inorganic 

 actions and reactions have taken place without man's aid, the 

 production of chemical compounds of one-sided asymmetry must, 

 on Prof. Japp's view of the relation of mechanical action to 

 chance, undoubtedly have taken place. Further, according to 

 Prof. Japp's fourth principle, we may look upon such asym- 

 metrical compounds when they have once arisen as " breeders," 

 or endowed with a power of selecting their own kind of 

 asymmetry from other racemoid substances. Let us put this 

 further statement on one side, however, and content ourselves 

 solely with dissent from Prof. Japp's view expressed in the 

 words : 



" But the chance synthesis of the simplest optically active 

 compound from inorganic materials is absolutely inconceivable. 

 So also is the separation of two crystallised enantiomorphs under 

 purely symmetric conditions." 



On the contrary, if the theory expounded by Prof. Japp be 

 correct, the inorganic origin of optically active compounds is not 

 only conceivable, but it has a degree of probability which, how- 

 ever small, might be calculated when we know what is the 

 minimum number of molecules in a physically just sensible 

 solution, and what is the majority of enantiomorphs of one 

 kind which will give a just measurable amount of rotatory 

 polarisation. 



It will indeed be a great gain if Prof. Japp's address calls 

 more attention to this exciting subject, and leads to further 

 experiment and research. Karl Pearson. 



The Moon's Course. 



The annual course which the moon takes in company with 

 the earth round the sun was to me a long time a great puzzle, 

 as it is to many others, until one day I demonstrated it to 

 myself by the simplest method. Those who have some smatter- 

 ing of the heavenly bodies generally fail in their attempt to 

 draw the moon's orbit ; they find no explanation in popular 

 works, and even in books written by well-known authors the 

 subject of the moon's motion is altogether ignored. All that 

 is found is a circle showing the moon's phases, and it is this 

 circle which is fatal to the conception of the true orbit of the 

 moon : even very young readers see the impossibility of a dozen 

 or thirteen circles surrounding the sun. 



For myself, failing to find assistance in books, I readily 

 solved the problem by a practical method. I took a piece of 

 wire and placed a cork on each end. I then drew a line 

 on the table and advanced one, which I called the earth, 

 along the line ; the other cork necessarily followed it, and at 

 the same time circulated round the earth in accordance with 

 another force or motion given to it. Beginning with the moon 

 behind the earth and making it pass to the right, both advancing 

 forward, the moon made a curve until it reached the front of 

 the earth, and then the latter still advancing, took the moon 

 with it ; this came on its left side, and then making another 

 curve on that side, again reached the front ; the two curves 

 completing the orbit round the earth. 



My object in writing at the present moment is, that when so 

 many persons are spending their holidays at the sea-side and 

 there is much talk of the tides together with the moon, I take 

 the opportunity of demonstrating by a similar method the 

 moon's course on the sands. I make one person walk in a 

 straight line, marking this with a stick, which he drags behind 

 him, and I call him the earth. I then place another person, 

 the moon, at a given distance from the other, telling him to 

 advance also, and at the same time circulate round his companion. 

 Beginning behind, and taking the right hand, he goes forward, 

 making a curve until he gets to the front, then passes to the 

 left side and forms another curve just as in the other ex- 

 periment. The four quarters of the moon are in this manner 

 seen, and if the second person continually faces the earth the 

 moon's monthly revolution is also completed. 



As these demonstrations are made on a plane, the experiment 

 may also be shown in another way. I wind some wire thirteen 

 times (the number of the lunar months) round a cylinder, and 

 then take off the coil thus made. I pull it out into a helix and 



NO, 1508, VOL. 58] 



join the ends of the wire. The course of the moon is shown, 

 in the spiral, although no correct proportions are attempted. 

 This also gives some idea why the moon is sometimes seen on 

 the horizon and sometimes at the zenith ; the reason of which 

 is a great difficulty to young people, as they find nothing about 

 it in their books. 



I make no pretence to be an astronomer or mathematician, 

 and, indeed, it may be even a presumption to send this com- 

 munication to a scientific journal ; but if those who can teach 

 fail to do so in popular books, there is no other method for the 

 uninitiated to do the best for themselves. Samuel Wilks. 



Grosvenor Street. 



The Aurora of September g. 

 This evening, at about three minutes past eight, on looking 

 out towards the south-west, I was struck by the appearance of 

 a shaft of white light stretching from that direction upwards 

 towards a point io° or 20° south of the zenith, and immediately 

 on reaching open ground, whence a wide view was obtained, 

 became aware that a fine display of aurora borealis was in pro- 

 gress. The shaft of light successively appeared and disappeared 

 at intervals of a few seconds, and each time further eastwards, 

 but each section was separated from the last by a space of un- 

 illuminated sky, as if there were regular spaces in the course of 

 the beam incapable of being set aglow. Very soon after pass- 

 ing overhead the illumination became faint and disappeared 

 eastwards, but now a strong glow appeared again near the 

 horizon under a cloud south-west by west, and this rapidly 

 grew upwards, repeating the phenomenon described in the first 

 case. This occurred at least eleven or twelve times with little 

 variation, except that the shaft became broader and more 

 diffuse. The glow near the horizon south-westwardr, was always 

 followed by the passage of the light across the sky within i 

 to li mins. , and each travelling beam was separated from 

 the last by an interval of i^ to 2 mins. Meanwhile the 

 sky north-westwards showed a pale white steady auroral light, 

 which was at first attributed to the remains of twilight, but 

 which continued to increase till about 8.30, when it was 

 sufficiently strong to cast shadows and to show large print 

 distinctly. This illumination extended slowly upwards from the 

 north until it covered a great part of the sky up to the zenith, 

 and seemed to be due to the luminosity of the great sheet of 

 cirrus and cirrostratus which had covered the sky since 3. 30 

 p.m., for it exactly imitated the distribution forms of the cloud 

 which I had noted during the afternoon. This cloud, unillum- 

 inated, did not appreciably obscure the stars. The lacunce of 

 dark interspaces, while the surrounding sky shone with pale 

 light, resembled bands or puffs of dark smoke, but remained 

 fixed in the same situation, and altogether the phenomenon was 

 strangely persistent, the only evident changes being a gradual 

 shifting from north-west to north-east, and at about 9 p.m. a 

 rosy streak north-eastwards. A little later fresh rays were 

 shooting up from north-west by west, somewhat resembling 

 those which an hour previously had emerged from south-west 

 by west, but more steady and unbroken. At 9.55 a faint light 

 was still to be seen in a north-westerly direction. Two hours 

 before this grand exhibition we had been able to get a good 

 view of the large spot on the sun, the intervening bank of 

 cirriform cloud making his appearance through a telescope more 

 like that of the moon. I have not seen any authoritative 

 statements as to interruption of telegraphic messages or other 

 magnetic disturbances coincident with or preceding the visible 

 aurora, but no doubt some effect must have been observed. 

 Dunrozel, Haslemere, September 9. Rollo Russell. 



A White Sea. 



During the recent voyage of the P. and O. Co. s.s. India to 

 London I had an opportunity (owing to the kindness of Captain 

 Worcester) of witnessing what seems to be a rare phenomenon. 

 The commander had seen it two or three times in the course of 

 his experience. No one else on board knew anything about it, 

 and I should be glad of a reference to any detailed description. 



At 1.30 a.m. on the morning of August 22, in the Indian 

 Ocean, the officer in charge saw ahead what seemed to be a low 

 mist, and into which the vessel steamed. I was called about 

 fifteen minutes later. 



The whole sea was milk-white, much more luminous than the 

 clear, starry sky, and there was a very definite horizon. 



