NA TURE 



[January 2, 1902? 



LETTERS TO THE EDITOR. 

 \Tlif Edilor does not hold himself yesponsihic for opinions ex- 

 pressed hy his correspaitdciils. Neither can he undertake 

 to return, or to lo) respond with the writers of, rejeitei 

 :naniiscripis intended for this or any other fart of Natuke. 

 No notice is taken of anonymous conimunications.'\ 



Kites and Wireless Telegraphy. 



In view of the current report in the daily Press that Mr. 

 Marconi has succeeded in receiving at St. John's, Newfound- 

 land, by means of a wire raised with a kite, signals sent from 

 his station at Poldhu, Cornwall, it may be interesting to recall 

 that kites were used here during the summer of iSgg in some 

 similar experiments. In the " Report of S. P. Langley, 

 Secretary of the Smithsonian Institution, for the Year ending 

 June 30, 1900," it is stated on p. lo : "In addition to the 

 above investigations a Hodgkins grant has been approved to 

 enable Mr. Rotch to carry on a series of experiments in space 

 telegraphy, it being thought that the unprecedented heights 

 attained by kites might materially extend the range of com- 

 munication by this method. In the preliminary experiments, 

 however, kites were not used, sufficient elevation being attain- 

 able without them, but when the difference between the stations 

 was increased from one mile to three, kites were employed to 

 raise the transmitting and receiving wires. In the later experi- 

 ments it was found, nut unexpectedly, that the long wires, 

 carried up and supported by kites, collected so much electricity 

 as to interfere with and greatly complicate the messages sent 

 from station to station. The.se interruptions seem to show that 

 the limit of elevation for the receiving wire was under these 

 conditions less than five hundred feet. The greatest distance 

 covered in the experiments was approximately twelve miles, 

 from a wire supported by a kite about two hundred feet above 

 Blue Hill to the tower of Memorial Hall in Cambridge, which 

 was used as the receiving station. These experiments draw 

 attention to the fact that electrification increases with the 

 altitude to which the wire is carried, and that it is always 

 present, although varying with the meteorological condition of 

 the atmosphe'e. The experiments were discontinued in the 

 autumn of 1899." 



If Mr. Marconi, by his system, has really received signals 

 from across the Atlantic, with the receiving wire lifted by a 

 kite to an altitude exceeding five hundred feet, it would appear 

 from my experiments that he must have employed some hitherto 

 unknown method of shunting out atmospheric electricity. 



A. Lawrence Rotch. 



Blue Hill Meteorological Observatory, 

 Mass, U.S.A., December 17, 1901. 



Poisonous Molluscs. 



I NOTICE that doubt is cast on the opinion held by some autho- 

 rities that the bite of certain species of Conus is poisonous ; 

 and as a case has now occurred here in a European subject 

 whose intelligence places her account of it beyond question, I 

 think it may be useful to represent the corroborative evidence 

 thus obtained. 



I should mention, first, that a shell exactly similar to the one 

 in question was forwarded 10 the Australian Museum, Sydney, 

 and that I am indebted to Mr. Etheridge, the curator, for in- 

 formation on the point and for the identification of the specimen 

 as the shell of Conus geographiciis. 



The patient, Mrs. B., was fishing from a boat after dark in 

 the harbour of Levuka (Fiji), and one of the crew handed her 

 a mollusc he had picked up in shallow water at low tide while 

 getting bail — a C geogi-aphiais. Mrs. B. , being an old resident 

 in the islands, proceeded to evulse the mollusc with her little 

 finger, the boy having cracked the shell to facilitate this pro- 

 cedure. While doing so she received a puncture, and shortly 

 afterwards felt her hand and fore-aim becoming numb. The 

 effect quickly extended to the shoulder, and the patient had to 

 return to the shore and be conveyed home. In an hour or so 

 she was in great distress, speechless, and paralysed in most of 

 the voluntary muscles ; a condition which later became inten- 

 sified and alarming, although the cardiac and respiratory muscles 

 showed no evidence of flagging. The medical man who at- 

 tended Mrs. B. likened her condition to that which might be 

 looked for after jioisoning by ttirare. 



The puncture was so slight as to be scarcely discernible ;. 

 after two days a steady but slow recovery took place, and a 

 fatal termination was averted. 



During this time the patient did not lose consciousness ; but 

 there was for a while some confusion of ideas, and, chiefly in 

 consequence of the loss of power in the muscles concerned in 

 articulation, she was unable to speak intelligibly, although she 

 subsequently asserted that she knew quite well what was going 

 on around her. She underwent an attack of conjunctivitis a. 

 few days later, which she connects with the occurrence ; but it 

 is doubtful whether she is right or not in so believing. 



R. Gl.AN\JLL CORNEY. 



Medical Department, Fiji, September 30, 1901. 



The Distance of N^va Persei. 



It appears to me that the phenomenon of the apparent' 

 expansion of the nebula surrounding Nova Persei would be 

 simply explained by referring it to the illumination of meteoric 

 matter by the light sent out on the occasion of the outburst of 

 the Nova. On this hypothesis it becomes possible to calculate 

 the distance from the earth by means of the observed angular 

 growth of the illuminated ring which must spread out with the 

 velocity of light. This gives 313 light-years as the distance. 



Daramona. W. E. Wilson. 



Colours of Butterflies not due to Diffraction. 



Some time ago your correspondent, Mr. Benham, corrected' 

 the mistake that mother-of-pearl owes its beauty to diffracted' 

 light. The error had lived long, partly, perhaps, because it 

 came from an authority so eminent as Sir David Brewster. 



A similar idea seems to be still prevalent, that butterflies and' 

 moths derive their colours from diffraction. Two of the best 

 modern natural histories, which I. have at hand, favour the 

 supposition. 



The patches on the wing are groups of uniformly coloured 

 scales, which contain pigment. Diffraction colours are of a differ- 

 ent character ; they are many-coloured iridescent lights varying; 

 as they glance off at different angles. The distinction is familiar 

 to a worker in optics ; it is easy for anyone to appreciate it by 

 seeing recognised forms of diffraction. I; have lately examined' 

 a collection of British Lepidoptera, and found no specimens 

 which were coloured by wave interference. The Purple 

 Emperor has two uniform colours, greyand purple, .so arranged 

 that there is a direction of vision favourable for seeing each .. 

 colour. Shot silks and Labrador spar are cases somewhat 

 similar. I have before me a foreign Thecla which has a 

 brilliant light-blue pigment; perhaps- in this and some others- 

 a certain shimmer is added by a slight diffraction interference, 

 but the predominant effect is the blue colouiingmatter. 



It is, however, interesting to note that all scales have fine 

 diffraction rulings. These lines, as in the case of diatoms, 

 consist of rows of small spots. Iihave had a wing of the Small 

 Tortoiseshell for about twenty years ;.the scales !are complete, 

 but the colours are faint, and the wing is i>artly transparent. 

 It is possible to arrange this with care in a strong light so that 

 brilliant rainbow lights are seen, but they' are not the familiar 

 tortoiseshell pattern. This effect does not seem to be possible 

 with a fresh wing, so that I doubt whether butterflies are often 

 seen to act as diffraction gratings. No doubt some insects .show 

 interference colours, but these seem usually to arise from the 

 phenomenon caused by thin plates. Diffraction can be well 

 studied in humming-birds ; there are the brilliant, ever-varying 

 lights, and the fine markings on the feathers may be seen with 

 a microscope. No iridescence is more delicate than that on the 

 side of a fresh mackerel. I am not quite sure to which class of 

 wave interference this is due. \Vi B. Croit. 



Winchester College, December 30, 1901. 



The Quadrantid Meteors. 



Nor the least important of our annual star showers are 



the (Juadrantids, so called from the position of their' 



radiant in the constellation of ijuadrans Muralis, which is • 



situated between Bootes and Draco. This meteor-system . 



NO. 1679, VOL. 65] 



