Dsa 30, 1881.J 



KNOWLEDGE 



183 



It seems hardly necessary to explain why the white paint shonld 

 become black. It is simply due to the action of the gas — already 

 alluded to above — on the white lead of the paint, sulphuretted, 

 hydrojjon having the property of changing the white lead or oxide 

 into the sulphide of lead. 



Bitumen is, I believe, tlirown up onto the shores of Callao, just the 

 same as it is on the shores of Mexico, where it soon becomes a hard 

 mass. F. C. S. 



COLOURS OF ANIMALS. 



PERMIT me to reply to " B. Donbavand," [let. 130] that hi.s 

 remark concerning floundcra being " concealed by acovering of 

 <r.iid'' is entirely beside the question ventilated in my paper on 

 < ''iour in animals. If your con-espondent has ever seen a sole or 

 'under, be must know how accurately the sandy hue is mimicked 

 V the upper side of the animals. — If ho had (as I doubt) ever seen 

 ^ ilounder lying motionless and uncovered in an aquarium tank, he 

 ■'■ ' 'uld never have penned his sweeping statement above referred to. 

 r.rmit me to say that I have repeatedly had the greatest possible 

 'litliculty, both in gazing into shallow water, and in aquaria, in dis- 

 tingui%liiDg the outline of flonndcrs of whose presence I was aware, 

 trom the sand on which they reposed. '" B. Donbavand's " remarks 

 n the " extreme tenuity " of scientific investigation (he might have 

 ;sed a plainer term than " tenuity ") strike at the root of all scien- 

 lic advance. Who, pray, is to decide what is important and what 

 - insignificant in scientific research ? Wlio can tell the bearing of 

 ven apparently the most trifling fact on future research? " B. 

 Ilonbavand " arrogates to himself just a little too much authority, 

 wlien he writes cynically of " extreme tenuity " in such a case as 

 Mr. Darwin' s observations on '* Worms." The single sentence in 

 ' B. D.'s " letter, wherein he speaks of Darwin's work as a " huge 

 paradox," is just a trifle too near silliness to warrant further 

 remark. 



In anffn"er to " Omithorhynchns " [100], who asks why the stings 

 of bees and wasps do not affect a toad when it swallows the insects, 

 1 may simply refer him to the common-sense explanation of very 

 plain differences between the constitution of a low vertebrate, such 

 as a toad or frog, compared vrith the higher warmblooded ver- 

 tebrates. Your correspondent is evidently thinking of the effects 

 of the insects' sting on the human type when he puts his question 

 r nnoerning the uumunity of the toad. But analogy reveals many 

 amples of the fact that the powers of different quadrupeds to 

 ■sist the evil effects of noxious foods, must be due to differences in 

 ihe nervous sensibility, and to other features in the constitution of 

 the animals in question. A donkey eats raw nettles, a dietary that 

 would kill a man by producing severe throat inflammation. A 

 ^'cretary bird devours serpents, which may contain poisonous 

 itter suflScient to kill a legion of birds; and man is in the same 

 sition as the bird, inasmuch as he can sivallow safely poisons 

 v.iuch only act when introduced directly into the blood-circulation. 

 In a word, individual or race peculiarities serve to render innocuous 

 to one animal what is a poison to another. Tlie black races of men 

 't'l not suffer from yellow fever, which kills off the white. A 

 ipical sun burns and blisters a white skin, but leaves the black 

 kin untouched. 

 The second Query [101] of "Ornithorhynchus," regarding" ants," 

 \Niil be best answered by referring him to Sir John Lubbock's 

 " Scientific Lectures " for a full exposition of what is known about 

 the habits of those insects. 



AXDEKW Witsox. 



SCIENTIFIC GHOSTS. 



THE following paragraphs are from the " Leaves from a Natu- 

 ralist's Note Book,"* by our esteemed contributor. Professor 

 Andrew Wilson, a work we can cordially recommend. It contains 

 articles (some of which many of our readers may have seen in 

 various magazines and journals) on many and very various subjects. 

 Giants, Kangaroos, Food and Pasting. Jelly Fishes, Whales, Science 

 and Crime, Leaves, ic, &c., all treated clearly and correctly, and 

 all treated in a most attractive manner. The subject we select for 

 extract is a good illustration of Professor Wilson's method : — 



Modem science has made us aware that the old belief in appa- 

 ritions rested on nothing more than illusive fancies caused by some 

 kind of physical derangement of the person so affected. It is im- 

 portant that young persons should be made thoroughly aware of the 

 tact that there never was and never will be any such fancy which 

 w not capable of being explained upon natural grounds. A person 



• " Leaves from a Naturalist's Note Book." Bv Andrew Wilson, 

 F.E S.E., kc. (Chatto & Windus, London.) Price 23. 6d. 



in weak health, though in perfect possession of all his faculties, 

 begins to be troubled by waking visions of persons with whom he 

 may be familiar, or who may have been long dead, or who sometimes 

 may appear as perfect strangers to him. The spectres who flit 

 before him, " come like shadows " and " so depart." They represent, 

 in the most perfect manner, the reproductions of things that are or 

 were — utterly intangible creations. The subject of these visitations 

 may hear the spectres converse, and they may even talk iu turn to 

 him. He is perfectly aware of their visionary nature, and is as 

 conWnced of their unreality as is the friend who sees them not, and 

 to whom the phantoms are described. No suspicions of insane 

 delusion as to these visitations can be entertained for a moment, 

 and the question may therefore naturally be i)ut to the naan of 

 science, " How can these illusions be accounted for ? " The answer 

 is to be found in one of the simplest studies in the physiology 

 of nerves and of mind, and shows us that these illusions have a 

 material basis, or that, in the words of the poet, the 

 " Shadow proves the substance true." 

 One of the most interesting cases of vision seeing by a person of 

 culture and intelligence is that related in the Athenirum of January 

 10, ISSO, by the Rev. Dr. Jessopp, who, in Lord Orford's librarj', 

 when engaged in copying some literary notes, saw a large white 

 hand, and then, as he tells us, perceived " the figure of a somewhat 

 large man, with his back to the fire, bending slightly over the table, 

 and apparently examining the pile of books I had been at work 

 upon." The figure was dressed in some antique ecclesiastical garb. 

 The figure vanished when Dr. Jessopp made a movement with his 

 arm, but reappeared, and again vanished when the reverend narrator 

 threw do\vn a book with which he had been engaged. Dr. Jessopp's 

 recital called forth considerable comment, and amongst others a 

 letter from the present writer, detailing the familiar theory based 

 on the principles of subjective sensations, treated of in the present 

 paper. After noticing the fashion in which subjective sensations 

 become projected forwards, the author sa3-s (Athenwum, January 

 17, 1880) : "The only point concerning which any dubiety exists, 

 concerns the exact origin of the specific images which appear as the 

 result of subjective sensory action. My own idea is that almost 

 invariably the projected image is that of a person we have seen and 

 read about. ... In Dr. Jessopp's case there is one fact which 

 seems to weigh materially in favour of the idea that the vision 

 which appeared to him in Lord Orford's library was an unconscious 

 reproduction of some mental image or figure about which the 

 Doctor may very likel3" have concerned himself in the way of anti- 

 quarian study." It is most interesting to observe that in the 

 succeeding number of the Athen(Tum, Mr. Walter Rye writes : 

 "Dr. A. Wilson's solution 'that the "spectre" . . . was an un- 

 conscious reproduction of some mental image or figure about which 

 Dr. Jessopp may very likely have concerned himself in the way of 

 antiquarian study,' seems the right one, and I think I can identify 

 the ' ghost ' The ecclesiastically dressed large man, with closely 

 cut reddish-brown hair, and shaved cheek, appears to me the 

 Doctor's remembrance of the portrait of Parsons, the Jesuit Father, 

 whom he calls in his 'One Generation of a Norfolk House,' 'the 

 manager and moving spirit ' of the Jesuit mission in England. . . . 

 Dr. Jessopp when he thought he saw the figure, was alone in an old 

 library, belonging to a Walpole, and Father Parsons was the leader 

 of Henry Walpole, the hero of his just-cited book. Small wonder, 

 therefore, if the association of ideas made him think of Pafeons." 



All such illusive visions are thus readily explained as the creatures 

 of an imagination which, through some brain-disturbance, is enabled 

 to project its visions forward, on the seats of sense, as the " ringing " 

 in our ears is produced by some irritation of hearing-centre of the 

 brain. The known vision is a reproduction of a present memory, 

 and the unknown vision is the reproduction of a forgotten figure 

 ^vhich has nevertheless been stored away in some nook or cranny of 

 the memory chamber. 



We may thus dispel the illusion by its free explanation ; and 

 science has no higher function or nobler use than when, by its aid, 

 a subject like the present is rescued from the domain of the 

 mysterious, and brought within the sphere of ordinary knowledge. 



A VEKY Impoet-^nt Gift has been made to the New York 

 Museum of Art by its President, John Taylor Johnston. It consists 

 of a collection of 331 engraved gems made by the Rov. C. W. King, 

 of Cambridge, England, a connoisseur and authority on glyptic art. 

 For the most part these antique gems follow in chronological order 

 the Di Cesnola collection, which Mr. King, in a treatise, called "a 

 true revelation in the history of glyptic art." Speaking of this 

 addition to the museum. General di Ce.snola said that with it two 

 more departments were now unsurpassed by any similar ones in the 

 great European Museums. Each of the pieces is accompanied by a 

 plaster cast. The catalogue is in Mr. King's handwriting, and a 

 treatise on glyptic art, by Mr. King, accompanies the collection. — 

 Frank Leslie's Magazine. 



