172 



NA TUBE 



[June 21, 1894 



other purposes. Considering the present rage for this 

 type of boiler, other examples might have been given 

 with advantage. 



LETTERS TO THE EDITOR. 



[TTu Editor does not hold himsel) rtsponstblt for opinions ex- 

 pressed by his correspondents. Neither can he undertake 

 to return, or to correspond -.vith the writers of, rejected 

 mmuscripts intended for this or any other part of Naturb. 

 No notice is taken of anonymous communications.^ 



The Hodgkins Fund Prizes. 



The time within which papers may be submitted to com- 

 petition for the Hxjgkiiis Funi Prizes of the Smithsonian 

 Institution, fjr essays in regard to the nature or properties of 

 atmospheric air, has been extended from July I to December 

 31, 189^,. This action has been taken (or the reason that 

 many of the circulars announcing these prizes seem to have ^ 

 (ailed to reach the persons for whom they were intended. j 



Numerous inquiries have been received, which render I 

 it desirable to announce that while it is preferred that 

 the name and address of each competitor should be 

 attached to the manuscript, any one who desires it, 

 is permitted to send his name and address in such a 

 form that they can be detached from the manuscript, which he 

 may identify by means of a motto. The manuscripts of un- 

 successful competitors will be returned wherever they have 

 been accompanied with the proper address ; but the proprietor- 

 ship of papers which have been awarded one of the named | 

 prizes, will rest with the Institution, which only desires to give 

 them a wide publicity ; and no copyright privileges are, in this 

 case, to be expected by the author. 



Papers which have been already published will not be ac- 

 cepted in competition for the prizes, but may be eligible for the 

 medal. This medal will be awarded in the same way that 

 medals are usually awarded by the principal scientific societies, 

 the medallists being chosen from all investigators known to 

 the Committee of .\ward, and not necessarily from among those 

 who have submitted papers. 



Information regarding the Hodgkins Prizes and the Smith- 

 sonian Institution may be obtained from the Secretary of the 

 Institution, S. P. Lingley, Washington, D.C., or from the 

 Agents of the Institution, Messrs. William Wesley and Son, 

 28 Essex Street, Strand, London. S. P. Langlev. 



Washington, June 6. 



Electrical Theory of Vision. 



I.s reference to the hypothesis concerning vision which I sug- 

 gested at the Royal Institution on June I, Dr. Obach has 

 favoured me with the enclosed letter detailing an observation 

 of his on his own eyes, which may be worth placing on record. 

 I therefore send it on to you. Oliver J. Lodge. 



University College, Liverpool. 



I.N your very interesting discourse at the Royal Institution on 

 Hertz's work, which is reproduced in Naiure of June 7, you 

 suggested that the susceptibility of the eye to light-waves might 

 be analogous to that of your "coherer" to Hertzian waves, and 

 that the light merely causes a diminution of electric resistance of 

 some badly-conducting material interposed between a source 

 of electricity and the sensitive nerves of the eye. The sensation 

 of darkness you explain by the return of the interposed body 

 to its original state, produced by an automatic tapping back on 

 the part of the tissues. 



In reference to this matter, I should like to bring to your 

 notice an observation, made some three years ago, which seems 

 to mc to support your views .is to the nunliis of>craudi of 

 the eye. One evening, aficr having watched the famous Rhine 

 Falls near Schaffhausen, for a con<.iderablc time in the full glare 

 of the sun, which produceti a dazzling whiteness of the spray, I 

 felt intense pains in the head and eyes, which did not diminish 

 much even after I retired to bed in a |>erfcclly dark room. I 

 ihereu; ^ 'I to a remedy, which had given me relief on 



previ'' with pain> in the eyes caused by overstrain, 



i.e., I ; J thumb and forefinger on the eyes over the 



closed eyelids and imparted gentle vibrations to the eye-balls. 

 After two or three vibrations I was compelled to stop, as the 



MO. 1286, VOL. 50] 



remedy was not only very piinful, but also produced the sensation 

 of a bluish-white light of dazzling brightness (like an electric 

 arc) being brought almost into contact with the eyes. After the 

 lapse of a few minutes the luminous phenomenon sub-ided, and 

 I again commenced the vibrations of the eye-balls, which now I 

 could do a little longer than before ere it became unbearable. 

 This operation I repeated, with intervals of rest, perhaps eight 

 or ten times, till finally the vibrations were almost painless and 

 produced no longer any luminosity ; the pains in the eyes and 

 head had then nearly disappeared, and I slept soundly the whole 

 of the night. 



The explanation of this curious observation seems to me the 

 following: — The intense brightness of the light reflected from 

 the spray had not only reduced the resistance of the intercepting 

 medium to a minimum, but at the same time overtaxed the 

 elastic tissues whose duty it would have been to shake the 

 material back into its normal condition, after the cessation of 

 the light. The energy thus lost by the tissues was then 

 suppressed from wiihout by the vibrating fingers. 



For what reason the return of the intercepting substance to 

 its original insulating condition should also be attended by the 

 sensation of light is dilTi:ult to conjecture, unless it be directly 

 due to the physiological effect produced on breaking the 

 circuit. 



Similar effects, only not so pronounced, can be observed on 

 vibrating the eye-halls after any ordinary overstrain of the eyes. 



Old Charlton, Kent, June 10. E. OnACH. 



Ophiophagus. 



The family of the venomous snakes called Elapida; is divided 

 into two sections, the N.ajid.T;, or snakes with hoods, and the 

 ElapidjE, without hoods. The Najidje is represented by the 

 Cobras and Ophiophagus ; it has two genera, Naja and 

 Ophiophagus. 



The genus Ophiophagus has but one species, the Ophiophagus 

 claps, or Hamadrayas ophiophagus. This is probably the largest 

 and most formidable venomous snake knoA'n. In size and dead- 

 liness it rivals the Crotaline snake, Lachesis tiiulm, the liush- 

 master, found in South America. The Ophiophagus grows to 

 the length of 12 or 14 feet, or even more. It is hooded like 

 the cobra, and resembles it in configuration and character. The 

 colour varies according to age and locality, being some shade 

 of olive-green or brown; young specimen; have a different 

 colouring, and might easily be mistaken for another genus. 



This deadly snake, though widely distributed, is fortunately 

 not very common, and consequently its bile, though fatal, does 

 not contribute largely to the 20,000 deaths that occur annually 

 from snake-bite in India. It is found on the Indian Continent 

 and liurmah, in the Andaman and Philippine Islands, in Java, 

 Sumatra, Borneo, and perhaps in New Guinea. It is not known 

 1 much, if at all, in Notth-Western and Centr.il India ; it is more 

 common in the damp climates of Bengal, Burmah, Assam, and 

 Southern India. 



The Ophiophagus, like other snakes, takes readily to the 

 water. It is found in the forest and grass jungle and in hollow 

 trees ; it climbs readily, being frequently found in the branches. 

 As its name implies, it feeds upon other snakes, but probably, 

 when its usual food is not forthcoming, it will take small mam- 

 mals, birds, fish, or frogs. 



It resembles the cobra, except that it is longer in proportion 

 to its size, and that the hood is relatively narrower. The poison 

 is of a golden yellow colour. It is even more graceful in its 

 movements than the cobra, and turns more rapidly. The snake- 

 charmers in India prize it highly, but they say it is exceedingly 

 dangerous to catch and diflicult to handle before its fangs are 

 removed. It is said by the Rev. Dr. Mason, who knew it in 

 Burmah, to be very aggressive, and Cantor describes it as being 

 very fierce, and ready, not only to attack, but to pursue when 

 opposed. Its Bengali name is Sunkerchor. 



Three remarkably fine specimens of this rare snake have been 

 received at the Zoological Society's Gardens. A few years ago 

 a specimen died, which had lived for a long lime in the Gardens 

 and excited great interest. That and the individuals under 

 notice are probably the only specimens that have been brought 

 alive to this country. 



It will be of interest to numbers of naturalists and others to 

 know that this rare snake is now alive in the Society's Gardens, 

 Regent's Park, where it can be seen to great advantage in the 

 large and well arranged reptile-house. J. Favrer. 



London, June 12. 



