244 



♦ KNOWLEDGE ♦ 



[JA.H. 20, 1882. 



Iwiiigs with him, rcferencp was iiiadr (unconsciously, per- 

 haps, on tlic narrator's part) to sonic tradition of the passin;^ 

 away or full of the Draffon from its former niling position 

 among tlin constellations. Those who thus int<'rpret 

 ancient records (much more ancient tlian Jewish history) 

 find in Hercules, with his heel assailed \>y the serpent, as in 

 our constellation figures, the first Adam ; in 0[)hiuchus, the 

 serpent holder, the second Adam. In Argo they find the 

 Ark — in fact, in a whole series of constellations they find the 

 story of the Flood. In Aquariu.s, with the streams pouring 

 from his water-jug, they find the beginning of the Flood. 

 In the river Eridaniis and the seas in which PLsces and the 

 great sea monster, Cetus, seem to swim, they soi; pictured 

 the prevalence of deep water over the whole earth. The 

 Raven of tlie heavens is the Haven of the Flood-narra- 

 tive. Argo is the Ark, shown as if only the stern half 

 of a great ship lodged in the mountain. The Cen- 

 taur, bearing sacrifice, as Aratus says, to Ara, the altar, 

 is Noah oll'ering sacrifice after he had left the Ark ; and the 

 Bow of Sagittarius in the smoke (the Milky Way) which 

 seems to ascend from the altar, — 



Ara/i-ivi'.^ tliuris, stellis hnitaulibvs, iynem, — 



is the Bow of the Promise. 



These may, of course, only be fancies, but it is singular 

 how closely these constellations, which are among tlie few 

 really seeming to picture recognisable objects in the 

 heavens, correspond in seriuence and in range of right 

 ascension with the events recorded respecting the 

 Flood. For my own part, I am not of those who wonder 

 that the ancients should liave seen figures of the animals 

 and other objects with which they were familiar in the 

 heavens. From my boyhood upwards (and the boyhood 

 of the individual is like the childhood of the race) I have 

 seen figures among the stars, the figures being always 

 such as I was familiar with. Evoii so late as my recent 

 visit to the southern hemisphere, I found that almost 

 despite myself the novel-looking star groups formed 

 figures* with which I was ever after compelled to asso- 

 ciate them ; and I cannot doubt that it was the 

 same with the childhood of the human race. There 

 is certainly a well -shaped ship where Argo was 

 seen by the ancients ; the water streams of Aquarius 

 and Eridanus arc distinctly visible ; Ara is a well- 

 shaped altar; and though at present the figure of the 

 Centaur (the man part) is not so tipright as it was before 

 precession had tilted it over (as it has the ship), we can 

 still see there the figure of a portly man bearing something 

 towards the altar. The bow is clearly seen, and nothing 

 can be better in accidental picturing than the curling 

 streams of smoke (figured in the stars of the Milky Way), 

 which seem to ascend from the flat summit of t'lie 

 altar. 



But precession has altered the configuration of all the 

 star-groups as seen when most favourably situated for 

 observation. Take a star globe, and, holding it with 

 one forefinger near Thuban (Alpha Draconis), and the 

 other at the opposite point of the sphere, notice the con- 

 stellations as they slowly rotate. Note how steadily the 

 ship sails past its highest point, on upright keel ; how 



• I li.->d always oxpoctotl, from Sir John Ilcrschcl's description, 

 to find Orion wlicn inverted, as wo see liim in tlie southern skies, a 

 very noble and imiires-sivo lig-nre. But the very first time I so saw- 

 it, I immediately recognised in the tigure, Clivo Newcomc's picture 

 ot Fred Bayham, and I never afterwards saw the constellation 

 without at once seeing in it that ridiculous figure. When people 

 tell me they cannot see a Bear in Ur.sa irajor, I can only wonder at 

 their blindness ; the head of the bear being to mo as obvious and as 

 obviously ursine as a group of stars could well be. 



upright the Centaur and the Altar ;* and how many groups, 

 now almost unrecognisable, are seen in their new aspect to 

 bo fairly entitled to the names which the ancients 1x.'Stowed 

 upon them. 



SEEING THROUGH THE HAND. 



AN OPTIC.VL ILLUSIO.V. 



By Tho.m.vs Foster. 



rpHERE is a series of illusions affecting the apparent 

 JL shapes and positions of solid figures — not only regular 

 geometrical figures, as prisms, parallelopipeds, Ac, but all 

 solids whatever — drawn as if fonned of a transparent 

 material, .so that their farther as well as their nearer out- 

 lines or edges can be seen. It can be readily shown that 

 there is a law connecting in e\ery ease the false figure 

 with the real figure. I have prei)ared a paper on illusions 

 of this sort, with suitable illustrations, and another paper 

 witli illustrations on some curious cases of apparent motion 

 in sets of concentric circles. But these and other papers 

 on illusions are, it appears, kept over for the present by the 

 pressure of other matter. [Circles next week. — Ed.] 



In the meantime, I wish to submit to readers of Kxow- 

 LEDGE (as occupying less space) an illusion which seems 

 to me exceedingly instructive, as bearing on the question 

 how we see. Everyone knows that the eye itself is simply 

 the organ by which the optical nerve is affected by light, 

 and that it is liy this nerve that the brain becomes cogni- 

 sant of these light eflects, the brain interpreting the mes- 

 sages brought along the optica! nerve into information 

 respecting the objects of sight. 



Now the tw^o eyes, and the optical nerves which extend 

 to each, convey at all times different messages to the brain, 

 which yet, as a rule, combines the two sets of messages 

 into a consistent account (so to speak) of what is seen 

 with both eyes. Even when the eyes differ in focal length, 

 so that, as separately analysed, the views obtained by the 

 two (^yes are utterly unlike, the mind is very seldom per- 

 plexed by the two different accounts conveyed to it. But 

 fti the following experiment the eyes entirely deceive the 

 mind, conveying to it the. absurd impression that there is 

 a hole right through the palm of the hand, or of a book 

 or other opaque object which may replace the hand in the 

 experiment. 



Roll a slieet of card or paper (or the number of K>'OW- 

 LEDGE now in your hand) into a tube nine or ten inches 

 long, and about an inch in diameter. Holding this tube 

 with the right hand, say, look through it with the right 

 eye, while the left hand is held six or seven inches from 

 the eye, the palm facing you, and touching the tube a little 

 below the lowest joint of the little finger, that is, at about 

 the level of the middle of the palm. Then, if both eyes 

 arc open, the tube being held touching or close to the right 

 eye, while the left eye looks at the left palm (at about the 

 nearest distance for distinct vision), the appearance pre- 

 sented is as though there were a circular hole about an 

 inch in diameter through the palm of the left hand. 



Now, in this case, the mind does not need to be told 

 that it is deceived. The observer knows as well as possible 

 that while he seems to be looking with the left eye through 

 the palm of the hand at objects beyond, he is in reality 

 looking at those objects with the right eye through the 

 tul)e. Yet the mind does not correct the illusion, clearly 

 though it recognises that there is illusion and its nature. 

 The illusion is as preposterous as that experienced when 



• Only the modern figure of the Altar is absui-dly drawn upside 

 down. In old globes and charts we find it properly drawn. 



