July i6, 1903] 



NATURE 



247 



absolue." Under the term Culex, I think he means to 

 include also gnats of the genus Stegomyia. 



I have received confirmatory evidence from a gentleman 

 in Egypt, who says that he was recently able to sleep at 

 Ismailia without mosquito nets. 



The campaign against Culex at Ismailia originally 

 promised to be a difficult one, owing to the large number 

 of sewage-cisterns under the houses, and the result shows 

 how easily a simple and obvious idea like that of diminish- 

 ing mosquitoes by dealing with their breeding places can 

 be acted upon by an intelligent and effective executive 

 which sets to work at once, instead of wasting time on 

 useless discussions — as, for the most part, we have been 

 doing in British possessions during the last four years. 



It is to be hoped that, following the work of Gorgas at 

 Havana, and Logan Taylor at Freetown, the result at 

 Ismailia will be accepted as clinching the proof of the fact 

 that Culex, at least, may be materially diminished in 

 tropical towns. Ronald Ross. 



Liverpool, July ii. 



Translation of letter, dated July 2, from M. le Secre- 

 taire g^n^ral de la Compagnie universelle du Canal mari- 

 time de Suez, Paris, to Major Ronald Ross, Liverpool 

 School of Tropical Medicine : — 



" Sir.^I have the honour to inform you that, following 

 your mission of last September, numerous works of drain- 

 age and filling up of ditches have been effected, and that 

 a permanent department has been created for the purpose 

 of oiling cisterns and pits and suppressing marshes and 

 pools of water amongst the habitations of Ismailia. More- 

 over, measures of prophylaxis, consisting of the gratuitous 

 distribution of quinine and arsenic, commenced in the 

 month of April, 1902, are continued without interruption. 



" Since last December, the number of cases of fever has 

 very sensibly diminished by comparison with previous 

 months and with the corresponding period of last year, 

 and this decrease is maintained until to-day. 



" Owing to the time at which the sanitary works were 

 undertaken, the complete disappearance of the Anopheles 

 is not yet realised, but it can be stated that recently 

 captured insects have not been infected — which can perhaps 

 be attributed to the fact that the number of cases of fever 

 have been considerably reduced. 



" On the other hand, it is interesting to note that, thanks 

 to methodical petrolage, and to the incessant surveillance 

 of the breeding-places of mosquito larvae, the mosquitoes 

 called Culex have been suppressed in a manner almost 

 absolute, and that, in the hottest period of the year, it has 

 been possible to abandon the use of mosquito nets. 



" Regarding the consequence of these measures, a 

 definite statement cannot be made until after August to 

 November next, the principal malaria season. We have 

 every ground for hoping that the efforts with which you 

 have been so usefully associated will end in the complete 

 extinction of malaria in the town of Ismailia, and we will 

 communicate with you when we receive definite inform- 

 ation on this interesting subject." 



Another White Spot on Saturn. 



On July 9, at i4h. 4m., I observed another large white 

 spot in the northern hemisphere of Saturn, and on the 

 central meridian of the planet. The spot was quite bright 

 in contrast with the dark belt adjoining it, and a tolerably 

 easy object. I saw the spot again on July 12, when it 

 shone with a bright pearl-like aspect, and was estimated 

 on the central meridian at I2h. 50m. The marking is 

 much distended in longitude, and this makes it rather 

 dillicult to note its central passages accurately, but the 

 motion of the object seems decidedly swifter than the rate 

 usually adopted for the rotation period of Saturn. 



The following end of a bright extension on the eastern 

 side of the spot was on CM. at i3h. 35s. on July 12, and 

 a dusky patch between the N equatorial belt and the polar 

 shading followed at i4h. im. 



The markings above alluded to are quite different from the 

 bright spot seen by Barnard on June 23, and by myself on 

 July I. The present disturbance on Saturn seems to have 

 affected a very large area, and I have never observed any- 

 thing of the same conspicuous character on the planet in 

 past years. W. F. Denning. 



Bishopston, Bristol. 



NO. 1759, VOL. 68] 



The Thunderstorm of May 31. 



Mr. C. H. Hawkins, of Croydon, has sent me a copy of 

 a photograph of a lightning flash taken by him at " Addis- 

 combe," Croydon, on Whitsunday morning, May 31, at 

 2.30 a.m. 



The upper part of the main flash and the side flash both 

 show reduplication, and the photograph exhibits so many- 



Lightning discharge photographed at Addiscombe, Croydon, 

 on May 31, at 2.30 a.m. Direction N.N.W 



characteristic features that its reproduction may be of 

 service for comparison with other photographs. 



I therefore enclose a copy with Mr. Hawkins's permission. 



Meteorological Office, S.W., July 7. W. N. Shaw. 



THE LODGE-MUIRHEAD SYSTEM OF 

 WIRELESS TELEGRAPHY. 



THE system of wireless telerraphy which Sir Oliver 

 Lodge and Dr. A. Muirhead have been develop- 

 ing for some years has, within the past few months, 

 been brought to a degree of perfection which justifies- 

 the inventors in the belief that it is now of practical 

 commercial value. Thanks to the courtesy of Messrs. 

 Muirhead and Co., we have had an opportunity of see- 

 ing the system at work at a small experimental instal- 

 lation which has been put up in a field adjoining 

 Messrs. Muirhead's works at Elmers End, Kent. At 

 this station signals were being transmitted to and 

 received from a similar installation at Downe. The 

 distance betv^^een the two stations is only six or seven- 

 miles, but the chalky nature of the Kentish soil and the 

 fact that the station at Elmers End lies In a hollow 

 make this distance equivalent to eight or nine times 

 as much over water. Experiments which have been 

 made under the conditions which would obtain in the 

 practical application of the system for maritime work 

 and also over the Admiralty sixty-mile range have 

 shown that, with the same power and the same adjust- 

 ments as are required between Elmers End and' 

 Downe, thoroughly satisfactory communication can 

 be maintained across sixty miles of ocean. Considera- 

 tions of distance are, however, of secondary importance 

 in estimating the merits of wireless telegraphy systems, 

 for the recent work of Mr. Marconi and others has 

 made it clear enough that, given sufficient power, 

 almost any range can be attained. Trustworthiness,, 

 clearness, the design of circuits and apparatus, and 

 the possibility of successful syntonlsatlon are factors 

 of greater importance. Looked at from this point of 

 view, the Lodge-Mulrhead system presents severat 

 novel and interesting features which show that, though 

 it may be one of the latest to come into the field of 

 practical wireless telegraphy, it is likely to prove one 



