NATURE 



[Jan. 24, 1884 



oljserved to about one hour after the first after-glow had disap- 

 peared lielow the horizon. The exact moment of thi-; disappear- 

 ance has been more difficult to determine than in the earher 

 oliservations where darl<ness followed ; as recently the heavens 

 and the earth have been reilluminated jnst as the natural night 

 would have begun. T. Story-Maskelyne 



Salthrop, January 13 



As the "halo" exactly opposite the sun, reported by Mr. 

 T. W. Backhouse in Nature, January to (p. 251) may 

 prove to be of considerable importance, I beg to add my 

 observations of it on the 12th. I had noticed a mass of ruddy 

 colour under the given conditions, previously, but had not 

 detected its sti-ange nature. The sunset on the nth was very 

 fine. The 12th, until after sunset, was cloudless, except for the 

 hazy masses which seem to precede every sunrise, and, more 

 especially, sunset, at present. Our sunshine record is an un- 

 broken scorch from 9. 15 a.m. to 2.52 p.m. (sun seen clear of 

 horizon at 8.26, and touched at 4.0) ; I doulrt if, previously, we 

 have recorded even five hours in early January. At 7.45 a.m. 

 on the 1 2th (sun rose at 8.22) the cloud-glow had turned to 

 silvery gi-een below, and rose from 15° to 30° i 1 the south east. 

 At 7.47 the rose reached 60°, but was fainter. I first noticed 

 the " halo " at 7.52. It was then so well defined that, calling a 

 lady's attention by asking what she saw there, she spoke of it as 

 "abroad rainbow." Position, by compass, 30° north of west. 

 It was a semicircle situated 10° above the horizon, standing on 

 the dark gray arch of dawn, Jupiter being on a line with the base 

 of the left end of the rosy arch. The inner arc of this measured 

 10°, and the outer 24° in radius, but it spread out to 30° at the 

 base. The centre was of the same blue as the sky to the right 

 and left of the rosy semicircle, above the gray. The base, 

 sinking faster than Jupiter, spread out so that, at 8 o'clock, the 

 arch havmg now broken above, its outline was rather like a 

 railway chair. The base now reached from west-north-west to 

 north-north-west by north. After sunset there were signs of a 

 similir phenomenon, but clouds prevented certainty. 



Is no\. fijiy miles an undMestiniate for the altitudes of the 

 light-reflecting material? If Mr. Symons is nearer the mark 

 in his suggestion (100 to 200 miles), then mure than half of 

 the eastward velocity of the original erupted dust is accounted 

 for by retardation, due to matter having velocity belonging 

 to an earth radius of 4000 miles, revolving in a circle of 4100 to 

 4200 miles radius. Would it need an eruptive force of more 

 than two to four miles per second (six to twelve limes greater 

 than a cannon ball) to attain tuch altiiudes? The constant 

 uprush would minimise the air-resistance enormously. 



Vork, January 14 J. Edmund Clark 



P.S. — January 15. — This morning, at 7.47, the "halo " began 

 to form, but was not nearly as perfect as on the I2th. The arch 

 (upper part only) v\as rayed, as if it were the opposite point of 

 siuht for rays from the sun. All over before 8, or fully twenty 

 minutes before sunrise. — J. E. C. 



With reference to Herr Wetlerhan's inquiry as to the absence 

 of the sky-glow in a clear sky at other places than Freiburg on 

 the morning of January 11, I find that at San Remo, in Northern 

 Italy, where I spent the week ending on that day, a similar 

 falling ofif of effect occurred at the same time. The sunri-e was 

 "very fine, but nothing to compare with the sunset of yester- 

 day," and "the filmy streaks were very thin, and stretched this 

 morning from south-west by south to north-east by north." 

 Nevertheless there was the strange bluish- white glare above the 

 eastern horizon, casting shadows, and a thin pink film up to 

 about 75° at 28 min. before sunrise. The sunset glow of this 

 day and of the day before was magnificent, the procession of 

 colours beginning about 15 min. after sunset, and lasting a full 

 hour. I see that your Constantinople correspondent also 

 mentions the sunset of the nth as a remarkably fine one. The 

 air on the loth, not the nth, as at Freiburg, was wonderfully 

 transparent at San Remo, the whole range of Corsican moun- 

 tains, over eighty miles distant, standing out sharply for 15 

 min. before and after sunrise, and the sun himself bursting forth 

 in great splendour from below the sea line. 



London, January 19 F. A. R. Russell 



Unconscious Bias in Walking 



Some ten or twelve years ago I made some experiments upon 

 the subject of Mr. Larden's letter in Nature (Jan. 17, p. 262), 



namely, unconscious bias in walking. Tho experiments were; 

 not numerous, but they left no doubt in my mind as to the cause 

 of divergence from a straight path. My n >tes were sent, at my 

 father's suggestion, to the late Mr. Douglas Spalding, who was 

 about to undertake experiments on the curious power which 

 animals have of finding their way. I rather think he made 

 some trials with pigs, but I believe he never published anything 

 on the subject. In stating my results I am compelled therefore 

 to rely on memory only. 



I began «iih walking myself, and getting various friends to 

 walk, with eyes shut in a grass field. We all walked with 

 amazing crookedness in paths which were not far removed from 

 circles. I myself and Mr. Galton on the first trial described 

 circles of not more than fifty yards in diameter, although we 

 thought we were going straight, and afterwards I was generally 

 unable to impose a sufficiently strong conscious bias in one 

 direction to annul the unconscious bias in the other. I believe 

 we all diverged to the right excepting one of us who was strongly 

 left-handed. 



I then got eight village schoolboys, from ten to twelve years 

 of age, and offered a shilling to the boy who should walk 

 stroightest blindfold. Before the contest, however, I dusted 

 some sawdust on the ground, and after making each of the boys 

 walk over if, measured their strides from riglit to left and left to 

 ri^;ht. Ihey were also made to hop, and the foot on which they 

 hopped was noted ; they were then made to jump over a stick, 

 and the foot from which they sprang was entered ; lastly, they 

 were instructed to throw a stone, and the hand with which they 

 threw was noted. Each of these tests was applied twice over. 



I think they were all right-handed in throwing a stone, but I 

 believe that two of them exhibited some mark of being partly 

 left-handed. The six who were totally right-handed strode 

 longer from left to right than from right to left, hopped on the 

 left leg, and rose in jumping from that leg. One boy pursued 

 the opposite coarse, and the last walked irregularly, but with 

 no average differ, nee between his strides. When told to hop, he 

 hopped on one leg, and in the repetition on the other, and I 

 could not clearly make up my mind which leg he used most in 

 jumping. When I took them into the field, I made the boys 

 successively take a good look at a stick at about forty yards 

 distance, and then blindfolded them, and started them to walk, 

 guiding them straight for the first three or four paces. The 

 result was that the left-legged boys all diverged to the right, the 

 right-legged boys diverged to the left, and the one who would 

 not reveal himself won the prize. The trial was repeated a 

 second time with closely similar results, although the prize- 

 winner did not walk nearly so straight on a second trial. 



I also measured ihe strides of myself and of some of my 

 friends, and found the saaie connection between divergence and 

 comparative length of stride. My own step from left to right 

 is about a quarter of an inch longer than from right to left, and 

 I am strongly right-handed. 



Comment on the-e experiments seems needless, and they 

 entirely confirm Mr. Larden in his view. 



It seems to be generally held that right-leggedness is commoner 

 than the reverse ; this I maintain to be incorrect. I believe that 

 nine out of ten strongly right-handed persons ai-e left-legged. 

 Every aciive effort with the right hand is almost necessarily 

 accompanied by an effort with the left leg, and a right-handed 

 man is almost compelled to use his left leg more than the other. 

 I lielieve that Sir Charles Bell considered that men were gene- 

 rally right-legged, and sought to derive the custom of mounting 

 a horse from the left side from the fact that the right leg is 

 stronger than the other. I suggest as almost certain that we 

 mount on that side because the long sword is necessarily w orii 

 on the left, and would get between our legs if we went to the 

 off-side of the horse. Some of your readers may perhaps be 

 able to tell us whether the Chinese do not wear their short 

 swords on the right and mount their horses from the right. 



I will not hazard a conjecture as to why the rule of the road 

 in Great Britain, and inside of the towns of Florence -and of 

 .Salzburg (?), is different from that adopted by the rest of the 

 world. For an armed horseman the English rule is, I presume, 

 more advantageous, both for attack and defence. 



January 20 G. H. Darwin 



The question whether a man will walk to the right or left in 

 a mist, in darkness, or if blindfolded, has led to n.i Utile con- 

 troversy and dispute. Almost every conceivable reason has had 

 its advocates for the fact that some men persi-tently turn to tlie 



