27G 



• KNOWLEDGE 



[Jav. 27, 18Sl 



upon it during; next simeou. Con80r\'utury flowora nre tho worst 

 possiblp tost in Buch n cn»i>, bccnimo tliey arc ospecinlly chosen for 

 tlieir lil(;l>l_v-<lnvol(>pt'(l |>etiil8 ; anil yet eleven instances examined 

 by Mr. Uowoe out of twenty-three, oven there liati yellow Mlanicnts, 

 while only seven IukI white, and five red. 



In answer to " I'lcsiosaunis " [1H:JJ, shonid nay that evergreens 

 novor had any origin. 'J'he real problem is exactly tho reverse — 

 tho oriffin of deciduous trees. Clearly any plant is benoHted by 

 having its leaves at work all the year round ; and all plants were 

 overKri'cns till a comparatively late KCological period, when the 

 poles began to frrow <olil. A few trees then acquired the habit of 

 deciduonsnoss, in ailaptation to tho new conditions, but to this day, 

 in the tro))ic8, evcrKroens aro universal. The process by which 

 decidaons leaves were developed I have already attempted to explain 

 in my little book, " Vignettes from Nature," and I will not attempt 

 to give the explanation over again here. Gbakt Allen. 



IXFI-UKNCE OF SEX ON MIND. 



[240] — Under the above heading, " J. McGrigor Allan " m.ikos 

 the following assertion — " Women lack the highest quality of the 

 human mind- justice." If this be true, how ia it that Shakespeare 

 and Sir Walter Scott, to say nothing of lesser men, have left so 

 widely different a testimony respecting the dignity of woman. To 

 quote the words of one of tho most polished writers of the present 

 day, " Shakespeare represents women as infallibly faithful and wise 

 counsellors, incorruptibly just and pure examples, strong always to 

 sanctify, even when they cannot save." In Sir Walter Scott's 

 imaginations of women, we find (with endless varieties of grace, 

 tenderness, and intellectual power) a quite infallible sense of dignity 

 and j««(ice. Aro these immortal writers wrong, and J. McGrigor 

 Allan right, or yice rerm ? Will you or any of your readers answer 

 this question, and oblige one w ho is — Only a Wom.\.\. 



WINDMILL ILLUSION. 



[241]^TIic Windmill Illusion, p. 233, reminds mo of two some- 

 what similar illusions I have noticed : — 1. The " governors " of a 

 steam-engine appear to rotate either way you please ; 2. The 

 same with tho " i)araUel rods" of a locomotive when seen from 

 a railway-carriage near the engine. 



Perhaps " Enquirer," Query 1U6, p. 234, may be glad to know of 

 the Dot and Dash system of shorthand, invented by T. S. Noble, 

 which is considered by some to be more easily learnt than 

 Pitman's. Vkg.^. 



VOLCANIC PROJECTILES. 



[242] — In the article on Vulcanologr, pp. 120 and 130, it is 

 stated that Vesuvius sometimes exerts snch force as to project 

 matter aearly four miles high ; and, further on, it says astronomy 

 has taught us that the world is not, as was long believed, a liquid 

 mass surrounded by a thin solid shell. 



Now, with regard to the first statement, will yon, sir, kindly say 

 if there is any foundation or belief that this force and height has 

 ever upon exceptional occasions been greatly exceeded, and, if so, 

 whether you think it possible that such matter might be thro^vn 

 beyond the direct power of the earth's attraction, to return, per- 

 haps, at some future time in the shajje of meteoric stones, or 

 never ; also what height would be necessary for such matter to 

 attain to get beyond this attraction. 



With regard to the second statement, how does astronomy prove 

 that the earth is solid throughout ? John" Roise. 



POPULAR FALLACIES. 



[2'13]— Vou would indeed deserve the thanks of all sane peoples 

 if you could reason away fallacies as suggested (No. 203, page 233), 

 even if they only concern the familiar poker that does 7iot "draw- 

 up " tho fire. 



In some parts of Scotland nervous people think that to praise 

 their possessions will necessarily bring destruction upon the thing 

 praised. A man says his horse has never been ailing for a day, or 

 that he loves a favo\irite tree, or admires his wife's dross. He has 

 sinned in uttering his thonght, but if ho raps three times on the 

 table and says " I must not /orcv/jonfc myself," perhaps his horse 

 will not go lame, his tree will not be blovra down, his wife's dress 

 will not be torn. 



It would bo impossible to talk gravely of such a custom wore it 

 not for the repeated surprise with which one observes that educateil 

 {and religinm !) people still have a lurking belief in its efficacy, just 

 na they still have a lurking dislike to thirteen at a dinner table. 



M. McC. 



ANIMAL PHYSIOLOOY (TUB EYE.) 

 [241-] — In the adjustment of sight, found in the vision of birds, 

 the eye is peculiarly adapted for long and short sight. It is like a 

 cnp in shape, has bony substance in tho form of plates, extending 

 along tho top and b'jttom of the eye, forming a support of Iho 

 sclerotic or hard lining, stretching from the cornea to the back part 

 of the eye, along which the retina is spread. These plates contract 

 or distend at will, but when contracted, they press the humonr, 

 causing the coniea to protrude, and tho retina to recede from 

 the lens. Connected with this pressure, and alteration of humour, 

 there is a peculiarity in tho eye of the bird — a thing like tho 

 appearance of a feather, which enters the vitreous humour by tho 

 optic nerve, commonly called a pecten, from its likeness to 

 a comb ; containing a lot of blood-vessels, mixed with 

 pigment granules. The question is, what effect has this 

 upon the eye ? Whether it is subject to erection or distention on 

 being filled or deprived of blood, or does this pecten act as a sieve, 

 passing through it matter from the blood to feed the vitrcotis 

 humor ; or is it nsed in passing off what surplus humor there may 

 be, and forming it into blood? If so, in what manner does it 

 affect the vision ? Something of the samo kind is found in fish, 

 although situated differently, it being between the two layers of 

 choroiil, instead of entering into the vitreous humor, as in the ease 

 of birds. In an animal belonging to the highest class of mollusc-a, 

 there is a thin retina at the back of the eye, and at tho back of 

 this a choroid, while at the back of this again, is another retina, 

 apparently for some other purjioso than to receive imjircssions. 

 Is there any similarity between this and the pecten of the bird, 

 and what purpose do they perform ? George Beowx. 



SOLAR PUZZLE. 



[245]. — There could be nothing between the sunlight and the 

 window-blind, except such things as those you suggest ; but you 

 must admit that not one of them could obscure, in regular and very 

 slow snccession, about three minutes to each hole, and in a diagonal 

 direction, the sun-patches, and, be it remembered, without interfer- 

 ing in the least with the long horizontal patch of sunlight, or with 

 the two or three holes on the extreme right. Forgive me for my 

 pertinacity. I see the difficulty in arriving at any solution, and that 

 was why I wrote to Knowledge. One solution occurred to me ; it 

 was — could an insect have obscured the holes ? Possibly, but then 

 it could only have been one at a time, for to have three, or even 

 two of the holes obscured at once would have required an " animal." 

 I can't say an " insect," six inches long, at the least. A. T. C. 



A NEW FACT IN PRISMATIC ANALYSIS. 



[246] — With reference to the " Answers to a Correspondent " in 

 Knowledge, vol. 1, page 257, about the delay in furnishing more 

 " Blowpipe Lessons," I would reply that I have now sent four com- 

 munications to Knowledge, only one of which, apparently, has been 

 considered up to the publishing mark. 



It has just struck me that the Editor's complaint against too many 

 of us is prolixity. However, it is refreshing to see, by the Editor's 

 remark above-mentioned, that, in Bow-street language, " 1 am 

 wanted"; and so I have tho pleasure to enclose another "easy 

 lesson," with what may be termed a " telegraphic summary" of a 

 curious result, obtainable by anyone possessing a lens and a glass 

 prism on a sunshiny day : — 



sunbeam 



admitted 

 : itistoad 

 prism 



Venetian blind 

 of I spectrum 

 : why I green ? 



green 



Focus 



face pris 



beam | wit 



Hoping our '• no-rent " friends across St. George's Channel will 



admit this "bangs Ballagher" (i.e. Dr. F. G e) in scientifio, 



conciseness. — I remain, Ac, W. A. Ross. 



WE.VTnER FORECASTS (ABSTRACT). 



[217] — I use the forecast chart and remarks, in conjunction with 

 observations of tho general aspects of the weather and sky around 

 me. The value of forecasts tlius applied, which I hold to be tho 

 true and rational method, is, on the whole, satisfactory. "Bad 

 shots" aro exceptional. It is well known that persons constantly 

 out of doors — seamen, farmers, millers (wind), Ac. — become highly 

 sensitive to atmospheric changes, and aro able to judge fairly well 

 of impending weather. Knowledge of this kind is only gained by 

 long observation, and cannot bo communicated. 



Storm warnings are, as a matter of fact, of most use to seafaring 

 people ; crops must risk tho weather, favourable or unfavourable to 

 their growth. Weather-wisdom in harvesting is a great help in 

 securing cix)ps in sound condition. 



