Oct. 6, 1882.] 



KNO^A^LEDGE 



313 



eighteen delightful engravings of Xew Forest scenery, 

 executed from drawings hy .Mr. Short, who, living amidst 

 the lovely scenery of the forest, " has learned his art from 

 the great book of Nature," 



Mr. Heath's work is one which we can thoroughly 

 recommend as well to the lover of nature as to the student 

 of art and science. It is a most enjoyable book. 

 Moreover, it is as handsome in paper, type, and binding as 

 book can well be. Its price (considering the nature of" its 

 contents, and, in particular, its twelve charmingly coloured 

 plates, is very moderate. 



PHOTOGRAPHY AT HOME.* 



Of late years there has been a revolution in the art of 

 photography, through which not only has a great change 

 been brought about in the rate at which pictures can be 

 taken, but they can be obtained under much more pleasant 

 conditions. Instead of a dirty, messy, and half-poisonous 

 operation, it has become one which a lady can perform 

 without soiling her fingers. The little hook before us shows 

 how the new methods can easily be learned and applied. 

 It gives a brief sketch of the history of photography, 

 describes the wet and dry processes, and gives a number of 

 useful hints about the practical details. The writer points 

 out that the constant study of pictorial effects, the lights 

 and shadows cast by clouds, the changing tints of foliage, 

 and other phenomena of nature, cannot but raise tlie 

 artistic tone of the mind which practises them. He would 

 even advise parents to let their boys and girls pay some 

 attention to photography, which, if it be only looked upon 

 in the light of a hobby, is at once harmless, healthful, and 

 inexpensive. 



THE POLYTECHXIC Y. M. C. 

 INSTITUTE. 



LAST Christmas the Polytechnic was purchased by Mr. 

 Quintin-Hogg, and adapted to the purposes of the 

 Young Men's Christian Institute, at the sole expense of 

 :Mr. Quiutin-Hogg, the cost being more than £2.3,000. The 

 Institute devotes itself almost entirely to the requirements 

 of apprentices, young mechanics, carpenters, bricklayers, 

 cabinet-makers, engineers, plumbers, and so forth — work- 

 shops being prominent features in its system. The portion 

 of the Polytechnic which was formerly occupied by the 

 Small Theatre has been entirely rebuilt, and formed into 

 a fine suite of rooms, which are devoted to the chisses 

 in the science, art, and technical schools. Adjoiiung is 

 a well-fitted and well-furnished chemical lal)oratory. 

 The Central Hall— the home of the old diving bell -his 

 been converted into a magnificent gymnasium, which is 

 said to be the best in London. The Lecture Hall will 

 accommodate 1,.">00 persons. There is a tine library and 

 reading-room, with first-class lavatories, fitted with every- 

 thing a mechanic might require to avoid the necessity of 

 going home before attending the Institute or the classes. 

 The applications for admission are already largely in excess 

 of what had been anticipated. We have looked through the 

 syllabus of the evening classes in science, art, technical 

 and general subjects, with constantly-growing wonder at 

 the wide range and admirable selection of the subjects dealt 

 with. 



• Photography at Home ; its Appliances and Apparalm /oi 

 Amateurs. (Marion «t Co., London.) 



letters to tbr eiiitor. 



He cannot undertake to 

 ments of the vriter'n meaninq.'] 



ine Editor doesnol hold him,elfre,f,on,HI,for the opinion, o/k{$ eorrenondenf. 



...J-...1.- '- — -. — uieripla or lo eorreipond riH their rriter,. All 



as poaeiUe, contittentli/ vtthfuU and clear atate- 



All Editorial ccvi'" " ' 



all Buiinett cimm 

 llreet, IT.C. 



Alt Eemitlaneei. Cheque,, and Fo,t-Office Order, thould le made pavable to 



',' All letter, to the Edito' rill lie Kumhered. For conrenienc qf reference, 

 correirpondent,, rhen referring to ans letter, Kill oblige bf vienlioning it, uuxber 

 and the page on Khich it appear,. 



" In tnoitledge, that man only is to he ccntemDed and despised who is not in a 



state of transitio" Nor is there anjihiog more adverse to accuracT 



than tixity of opinion." — Faradat/. 



" Show me a man who makes no mistakes, and I will show jou a man who hu 

 done nothing." — Liebig. 



SIZE OF RISING IIOOX. 

 [579] — Your late articles on "Forms of Clouds" remind me of 

 a theory I have long since arrived at as to the cause of the mag- 

 nified appearance of the full moon at or near the horizon. It is 

 briefly this :— There are two skies with wliich the eye is famih'ar— 

 the cloud sky and the star sky, differing remarkably in shape 

 and in the objects they present to observation. The star sky 

 is hemispherical, and may be represented by a semicircle. 

 All objects belonging to it are apparently eqnidistant from the 

 observer, and each is of the same size, whether seen overhead or 

 near the horizon. Thus, sun, moon, and stars have no appreciable 

 difference of size, and when the atmosphere is clear, but little of 

 distinctness, in whatever part of the sky they are seen. The cloud 

 sky, on the other hand, as shown by your diagrams, may be repre- 

 serited as resembling a small segment of a very large circle. The 

 objects in it are comparatively near when overhead, and very 

 remote when at its extreme parts. Thus a large bird in its flight 

 becomes gradually smaller, and at length is lost in the distance, 

 and, similarly, the largest balloon, though clearly visible when 

 overhead, diminishes as it recedes, and becomes but a point at the 

 horizon, even though, all the while, it may preserve the same 

 vertical distance from the earth's surface. Now if in this cloud 

 sky a second balloon were to be seen near the horizon beyond the 

 clouds and other intervening object.^, and having its outliiie clearly 

 distinguishable and its angular diameter equal to that of the balloon 

 overhead, the observer would instantly feel conscious that such 

 balloon must be enormously larger than the other, and it would 

 scarcely require any further reasoning process to convince him that 

 this must be so. 



A precisely similar, though momentary, mental impression is 

 experienced when the clear broad surface of the rising moon looms 

 up behind the clouds and other intervening objects, such as distant 

 houses trees, ships, Ac, seeming, from its apparent proximity 

 and relative position to those objects, to be moving in the samo 

 atmosphere which encloses them. Instantaneously the observer's 

 mind refers the great luminous mais to the cloud sky, and, as he 

 suddenly recalls the well-romomberod dimensions of the same orb 

 when seen overhead, the comparison, just as in the supposed case 

 of the balloon, flashes on his perception and produces the curious 

 illusion referred to. If the observer now turns his back, anil, by 

 means of a small mirror, throws the reflected moon upward into her 

 proper sky, she resumes, at once, her wonted size, and the illasion 

 disappears. G. E. 



LOCAL WEATHER LORE. 

 [uSO]— In rejily to your letter on the above-mrntioned subject, 

 I send ynu three ape.tliegms, Ac, Ac— not, indeed, quite local, bnt 

 \yhieh you may not have heard of. They are : — 



First. — " Saturday's Moon comes seven vears too soon." 

 Now, I remember hearing that " saw " fixim my father one very 

 wild Saturday evening in early summer that' wo hud a walk 

 together, lie was a man of limited education, but of cinsiderablo 

 sense, dashed, however, with a little superstition, it might bo. I, a 

 young lad, in my assumed superior knowledge, ridiculed the notion; 

 but I recollect ihnt many years after, and father had joined the 

 "great majority," taking up an is.suc of a rc-^iectable local news- 

 paper, the Cor^ CoH<a'(u(ioii, I observed in it a lengthy article. 



