November 2, 1900.] 



SCmNCE. 



691 



moment there are established at these places 

 Mr. Marconi's latest appliances, so adjusted 

 that each receiver at one station responds only 

 to its corresponding transmitter at the other. 

 During a three days' visit to Poole, Mr. Mar- 

 coni invited me to apply any test I pleased to 

 satisfy myself of the complete independence of 

 the circuits, and the following are two out of 

 many such tests: Two operators at St. Cath- 

 arine's were instructed to send simultaneously 

 two different wireless messages to Poole, and 

 without delay or mistake the two were cor- 

 rectly recorded and printed down at the same 

 time in Morse signals on the tapes of the two 

 corresponding receivers at Poole. 



In this first demonstration each receiver was 

 connected to its own independent aerial wire 

 bung from the same mast. But greater won- 

 ders followed. Mr. Marconi placed the re- 

 ceivers at Poole one on the top of the other, 

 and connected them both to one and the same 

 wire about 40 ft. in length, attached to a mast. 

 I then asked to have two messages sent at the 

 same moment by the operators at St. Cather- 

 ine's, one in English and one in French. With- 

 out failure each receiver at Poole rolled out its 

 paper tape, the message in English perfect on 

 one and that in French on the other. When it 

 is realized that these visible dots and dashes 

 are the results of trains of intermingled elec- 

 tric waves rushing with the speed of light across 

 the intervening 30 miles, caught on one and 

 the same short aerial wire and disentangled 

 and sorted out automatically by the two ma- 

 chines into intelligible messages in different 

 languages, the wonder of it all cannot but 

 strike the mind. 



Your space is too valuable to be encroached 

 upon by further details, or else I might men- 

 tion some marvellous results, exhibited by Mr. 

 Marconi during the same demonstrations, of 

 messages received from a transmitter SO miles 

 away and recorded by an instrument in a closed 

 room merely by the aid of a zinc cylinder, four 

 feet high, placed on a chair. More surprising is 

 it to learn that, whilst these experiments have 

 been proceeding between Poole and St. Cathe- 

 rine's, others have been taking place for the 

 Admiralty between Portsmouth and Portland, 

 these lines of communication intersecting each 



other ; yet so perfect is the independence that 

 nothing done on one circuit now affects the 

 other, unless desired. A corollary of these 

 latest improvements is that the necessity for 

 very high masts is abolished. Mr. Marconi now 

 has established perfect independent wireless 

 telegraphic communication between Poole and 

 St. Catherine's, a distance of 30 miles, by means 

 of a pair of metal cylinders elevated 25 or 30 

 feet above the ground at each place. 



I need not enlarge on the possibilities thus 

 opened out for naval and military purposes. 

 The importance of this practical solution of the 

 problem of independent electric wave teleg- 

 raphy, in which each wireless circuit is as 

 private as one with a wire, is obvious without 

 comment. My desire is solely to mention the 

 above facts for the benefit of general readers, 

 whose minds will thus perhaps be eased of any 

 doubts lest this brilliant application of elec- 

 trical discoveries should, like some others, fall 

 short of satisfying the requirements of practical 

 use and be relegated to the region of imperfect 

 inventions or unfulfilled hopes. 



SPECIES OF MOSQniTOES COLLECTED FOB 

 THE BRITISH BIUSEVM* 



At the latter end of 1898 a committee was 

 appointed jointly by Mr. Chamberlain and the 

 Royal Society to exercise a general supervision 

 over a scientific investigation of malaria, and 

 it was then suggested that, in view of the con- 

 nection of malaria with mosquitoes, it would be 

 desirable to obtain exact knowledge of the dif- 

 ferent species of mosquitoes and allied insects 

 in the various tropical colonies. Acting on this 

 suggestion, Mr. Chamberlain at once issued a 

 circular despatch to the Governors of all the 

 Crown colonies, requesting them to take the 

 necessary steps to have such collections made 

 and sent to the Natural History Museum for 

 examination and classification of the specimens. 

 For the guidance of those who might be em- 

 ployed on the work, directions for collecting, 

 mounting and preserving the insects were drawn 

 up by the museum and distributed in the colo- 

 nies. As a result of these measures considerably 

 over 3,000 specimens of mosquitoes have, we 

 learn, been received at Cromwell-road up to 



* From the London Times. 



