340 



NA 1 LRE 



[Feb. 12, 1885 



CIVILISATION AND EYESIGHT 



IN his interesting paper on "The Influence of Civilisa- 

 tion upon Eyesight," read recently before the Society 

 of Arts, Mr. Brudenell Carter supports the commonly 

 received view that the vision of savages is far more 

 acute than that of civili-cd men. In some sense this is 

 doubtless true ; but that the eyes of savages, considered 

 merely as optical instruments, are greatly superior to our 

 own appears to be inconsistent with optical laws and 

 facts long since established by the labours of Airy, 

 Helmholtz, and other investigators. It is known to 

 physicists that the resolving power of an optical instru- 

 ment is limited by its aperture. With a given aperture 

 no perfection of execution will carry the power to resolve 

 double stars, or stripes alternately dark and bright, 

 beyond a certain point, calculable by the laws of optics 

 from the wave-length of light. With sufficient approxi- 

 mation we may say that a double star cannot be fairly 

 resolved unless its components subtend an angle exceed- 

 ing that subtended by the wave-length of light at a dis- 

 tance equal to the aperture If we take the aperture of 

 the eye as 15th inch, and the wave-length of light as 

 l-40,oooth inch, this angle is found to be about 2 minutes ; 

 and we are forced to the conclusion that there is no room 

 for the eye of the savage to be much superior in resolving 

 power to those of civilised physicists, whose powers 

 approach at no great distance the theoretical limit as 

 determined by the aperture. 



It has always appeared to me that the superiority of 

 the savage is a question of attention and practice in the 

 interpretation of minute indications, and that it is com- 

 parable with the acuteness of the blind in drawing conclu- 

 sions from slender acoustical premises. It would be an 

 interesting subject for investigation, but I should not 

 expect to find that when put to a direct test blind people 

 were able to hear sounds wholly inaudible to others. 



The increasing prevalence of short sight is a very 

 important matter, worthy of all attention. There is one 

 fact in connection with it which I avail myself of this 

 opportunity of mentioning, in the hope of inducing 

 scientific oculists to give it further examination. I find 

 that, though not at all short-sighted under ordinary cir- 

 cumstances, I become decidedly so in a nearly dark 

 room, seeing much better with spectacles of 36 inches 

 negative focus. In a moderately good light I see rather 

 better without the glasses than with them. From the 

 few observations that I have made I have reason to 

 believe that this peculiarity of vision is not uncommon. 

 With the aid of a set of concave glasses it is easy to try 

 the experiment in a room lighted with gas. The flame 

 should be gradually turned lower ard lower, so as to give 

 full time for the pupil to dilate, and for the eye to acquire 

 its maximum sensitiveness. In my own case the most 

 marked indication of better definition is the augmentation 

 of binocular relief. Rayleigh 



THE INTERNATIONAL INVENTIONS 

 EXHIBITION 



HP HE RE seems now little reason to doubt of the success 

 -*- of the South Kensington Exhibition of next summer — 

 success, that is, from an educational and scientific point of 

 view. What its financial result may be depends upon a 

 variety of circumstances, and perhaps, since it is very 

 improbable that there can be any serious deficit, while, if 

 there is a large surplus, its disposal will, as usual, form a 

 problem difficult of solution, this part of the question does 

 not really very much matter. That Londoners will have 

 a pleasant outdoor lounging place, that there will be 

 abundance of music, that the fountains will be as pretty 

 as last year and the gardens prettier, all this may be 

 taken for granted ; but there now seems every reasonable 

 expectation that we shall have more than this, and that 



j the Exhibition will be what it professes to be — a complete 



! illustration of the progress made in the application of 

 science to industry during the past twenty years. At all 



I events if it is not it will be the fault of the promoters, 

 since they have had so large a range of choice that it has 

 only been possible to find space for some third of the appli- 

 cants, and an enormous number of exhibits have been 



j rejected, not because they were unsuitable or uninterest- 

 ing, but simply because, when there was not room for all, 

 some must of necessity be excluded. 



To begin with, it was thought best to exclude, not only 



! the actual articles which were shown last year, but inven- 

 tions of the same class, and consequently there will be found 

 at South Kensington this year few, if any, exhibits relating 

 to food, clothing, or sanitation. It appears that this rule 

 has given rise to a certain amount of heart-burning, since 

 reference is found to all these heads in the official classi- 

 fication ; but it must be remembered that the announce- 

 ment was duly made at the beginning that the space to be 

 allotted to these and certain other classes would be strictly 

 limited, and then again it was impossible to foresee how 

 large would be the response to the invitations issued. 



I The task of selection has been a difficult, and indeed an 

 invidious, one ; but we think it will be found, when the 

 show is opened in May next, that this thankless task has 

 been performed with great judgment, and with a just 

 consideration of the claims of exhibitors on the one hand, 

 and the interest of the public on the other. 



We are glad to have heard that in none of the thirty- 

 one groups into which the inventions' half (we are not now 

 considering the musical part) of the Exhibition is divided, 

 have the applications been deficient ; in some they are 

 naturally better than others, but in every one there is 

 enough to provide a fair representation of the condition 

 of its particular industry, and of the improvements which 

 have been made in it during the limits of time with which 

 the Exhibition is concerned. Even this will doubtless be 

 a cause of complaint to those who believe that injury will 

 be done to our manufacturers by the opportunity given to 

 foreigners of imitating our wares and the methods by 

 which they are produced. This is a specious but a some- 

 what narrow-minded notion ; the early history of invention 

 is full of stories of the efforts of inventors to keep their 

 inventions secret, and the constant failure of such efforts 

 may be taken as one of the principal causes which 

 produced the modern Patent system, under which an 

 inventor is protected, so far as law can protect him, in 

 the enjoyment of the property he has created. There 

 are, of course, many instances of processes worked, and 

 successfully worked, in secret ; but these are the exception, 

 and on the whole it is found that inventors individually, 

 and industry generally, gain far more by a system of 

 publicity than by one of concealment. So it is with exhi- 

 bitions. It may be taken as tolerably certain that manu- 

 facturers who have any special process which they desire 

 to keep to themselves will not select that particular 

 process for exhibition, and that on the whole manufac- 

 turers find exhibitions profitable or they would not be so 

 anxious to engage in them. The suggestion that was 

 made by some wiseacre that the Exhibition should be 

 confined to untried inventions, so that manufacturers (who 

 of course have no other means of hearing of novelties in 

 their own trades) might have the benefit of seeing them, 

 does not, perhaps, call for serious refutation. If the curious 

 collection of rubbish which fills the big building at Wash- 

 ington, devoted to the. United States Patent Office, were 

 carted across the Atlantic, and placed in the Kensington 

 Galleries, it is a question whether the public would be 

 more bored, or the manufacturers less instructed. 



As would naturally be expected, in an exhibition of this 

 character, machinery will occupy a far larger proportion 

 of the space than on previous occasions ; we understand 

 that it has therefore been necessary to make consider- 

 able additions to the motive power provided for the 



