270 



NA TURE 



1 Jan. 22, 1885 



wards, and finding the number of deaf-mutes known to 

 exist among the ancestors of the present inmates of the 

 asylums. The family history of many of these is 

 appalling, such as " Grandfather, father, mother, and 

 other relatives " ; " father, mother, one brother, and five 

 uncles and aunts " ; two cases of " father, mother, one 

 sister, one uncle, and one aunt " ; two cases of " father, 

 mother, two brothers, and two uncles," and so on. In 

 one case as many as fifteen deaf mute relatives are 

 recorded. Genealogical trees are given of the families in 

 which deaf-mutism prevails, and the large proportion of 

 the members of those families who are congenitally 

 afflicted is most painfully illustrated. The surnames of 

 the inmates of deaf-mute asylums are analysed, and the 

 frequency is pointed out of the recurrence of many 

 strange-sounding names, such as " Fahy," " Hulett," 

 " Closson," "Brasher," '" Copher, ' " Gortschalg," &c, 

 apparently out of all proportion to the number of persons 

 bearing those names in the general population. 



The influences that promote the inter-marriage of deaf- 

 mutes are fully described. The isolation of their class 

 from the rest of the world is becoming more and more 

 complete. Each institution is a self-sufficing alma mater 

 where every member feels really at home, and with which 

 each member continues his connection in after years. 

 Gatherings of old pupils of both sexes, cotiversaziones, 

 and other social meetings are of frequent recurrence, and 

 what is most important of all, the highly-developed and 

 very conventional gesture language of the deaf and dumb 

 has already moulded them into a distinct nation. They 

 think not in words, but in abbreviated symbolic gestures, 

 and the sequence and association of their ideas is thus 

 compelled to be idiomatic and widely different from those 

 of the rest of their race. English and other spoken 

 languages are foreign tongues to them, and are acquired, 

 for the most part, very imperfectly. A separate mode of 

 life is so congenial to persons reared under such excep- 

 tional surroundings, and of such exceptional natures, that 

 unwise schemes have been from time to proposed, of 

 buying land in settlements for the deaf and dumb, where 

 they should reside and form a secluded society of their 

 own. They are content with their lot when they are 

 brought into contact with none but themselves, but 

 they are ill at ease, and feel themselves to be aliens, when 

 they are forced into the presence of the outside world. 

 What wonder ;hat they should shrink from it, and inter- 

 marry and strive to keep apart. 



The interest of this strange story is twofold. In the 

 first place it shows how- easily a marked and degenerate 

 variety of mankind may be established in permanence by 

 a system of selection extending through two or three 

 generations ; and, secondly, it is an instance in which 

 strong social, and possibly legislative, agencies are sure to 

 become aroused against unions that are likely to have 

 hereditary effects harmful to the nation. The advisa- 

 bility of various forms of restrictive measures is judi- 

 ciously and carefully discussed by the author, with the 

 general result that gesture-language should cease to be 

 taught, the oral system being enforced in its place, and that 

 the philanthropic custom of massing the deaf and dumb 

 together in separate societies, and of making their life 

 as happy as possible in those societies, should be strongly 

 discouraged. 



Instructive experiments on the rate at which a deaf 

 breed of animals could be formed, might be made by 

 breeding deaf cats, who are by no means inefficient 

 mousers, and who show no signs of discontent at their 

 lot. I may mention an observation of my own as 

 having some possible pathological bearings. It was this : 

 during a country walk I lunched at a roadside inn, where 

 I saw a female cat with blue eyes, and asked and found 

 that she was quite deaf, but was told that her kittens all 

 heard perfectly. The only one of them that had been 

 kept was in the room, and she certainly noticed my voice 



and other noises I made to attract her attention, just as 

 readily as other kittens. Then it occurred to me to try 

 her with the shrill notes of one of my little whistles, which 

 I had in my pocket-book. She was absolutely deaf to 

 these, and I doubt if she could have heard a note as shrill 

 even as the chirp of a sparrow. Cats, as I have elsewhere 

 observed, are eminently sensitive to shrill notes, so that 

 the deafness of this kitten was a noteworthy proof that 

 the imperfect stages of the form of hereditary deafness to 

 which she was subject consisted in the degeneration of 

 that part of the auditory apparatus which is concerned 

 in hearing shrill notes. I am told that no thorough 

 anatomical investigation has yet been made into these 

 matters, owing to insufficiency of subjects. It would 

 therefore seem that a breed of deaf cats might be very 

 acceptable to physiologists, and I have no doubt that 

 such a breed might be easily established on any small 

 and sparsely-inhabited island from which every hearing 

 cat had been removed. Cats will not breed in strict con- 

 finement, and their roving habits at night make it im- 

 possible, under ordinary circumstances, to keep their 

 breed pure ; but in small islands, under the paternal 

 despotism of a popular landlord, this and many analo- 

 gous experiments in breeding varieties of small and 

 hardy animals and plants, such, I mean, as would take 

 care of themselves, might be carried out. I have often 

 envied the facilities afforded to such projects by the geo- 

 graphical and social condition of the Scilly Islands. 



Francis Galton 



ASTRONOMICAL TELESCOPES FOR 

 PHOTOGRAPHY* 



II. 



"HPHE simplest form of the reflecting telescope is that 

 -*- in which only one reflecting surface is used, known 

 as the Herschelian, or, as Sir John Herschel, in his work, 

 " The Telescope," calls it, " the Simple Reflector." The 

 remarks he makes on this form are well worth most 

 careful consideration in connection with the use of the 

 reflecting telescope for photography. 



All other forms have the second or third mirror only 

 for the purpose of bringing the image formed by the large 

 mirror where it can be more conveniently used. Of these 

 the Newtonian is the simplest and perhaps the best, as 

 here the second reflection does not alter the size of the 

 image, but only diverts it to the side of the tube. In the 

 Cassegrain or Gregorian form the use of the convex or 

 concave mirror enlarges the primary image more or less. 

 Modifications of the Cassegrain form can be made by 

 replacing the small convex mirror by a flat or very 

 slightly curved mirror, in which case, although there is 

 much loss of light, the image is kept nearly the same size 

 as in the Newtonian. There is also the "Brachy" form, 

 where the Cassegrain is used obliquely, but this is practi- 

 cally a Cassegrain. In all these telescopes, except the 

 first and last-mentioned, the second mirror requires 

 support of a kind that acts most injuriously on the 

 image, causing rays to come from stars which, in the case 

 of stars as faint as eight magnitude, show quite distinctly 

 with such long exposures as are needed in photographing 

 the nebula: or clusters of very faint stars. In addition to 

 these well-known forms of the reflecting telescope there is 

 the arrangement of three reflectors as a telescope indicated 

 by me in the May number of the Monthly Notices of the 

 Royal Astronomical Society, and also the application of 

 the Coude principle, treated of at length by M. Lcewy in 

 the June number of the Bulletin Astronomique (1884). 

 As far as I know there has not been any practical appli- 

 cation of the Coude' principle to the reflector. The need of 

 three reflections would involve great loss of light, and for 

 this reason alone would render it unsuitable for photo 



1 Continued from p. 40. 



