June 6, 1901] 



NA TURE 



131 



A, being connected through an inductance, >;, to the other 

 side of the spark gap. Mr. Marconi finds it essential 

 that the inductance of the two conductors A and a' should 

 be unequal, the larger inductance being preferably joined 

 to the non-earthed conductor A. Such an arrangement 

 proves both a persistent vibrator and a good radiator, thus 

 enabling selective signalling to be easily carried on over 

 considerable distances with quite short heights of cylin- 

 der. Very good results were obtained between the Isle 

 of Wight and Poole, a distance of three miles, with 

 cylinders i'5 metres in diameter and only 7 metres 

 high. 



Another very good syntonised transmitting and receiv- 

 ing system which has been devised by Mr. Marconi is 

 shown in Figs. 2 and 3. 



In this the terminals of the spark gap, B, are connected 

 to a closed circuit containing inductance and capacity ; 

 such a circuit is a very persistent oscillator, but a bad 



radiator and absorber. There is, therefore, combined with 

 it a good radiating circuit, consisting of the vertical 

 conductor, A, which is earthed through an adjustable 

 inductance, d. The vibrations set up in the primary 

 circuit connected to the spark gap mduce oscillations in 

 the radiating circuit, the mutual action being increased by 

 winding a part of the radiating circuit around the primary 

 circuit (at d'\ as in a transformer. The two circuits 

 are carefully tuned by adjusting either the capacity, e, or 

 the inductance, d, or both. In the receiving apparatus 

 (Fig. 3) the connections are similar ; the aerial wire is 

 connected to earth through an adjustable inductance, part 

 of which, p-, is wound as the primary of a transformer 

 of which the secondary, y-, is connected to the coherer ; 

 an adjustable capacity, h, is connected across the coherer 

 in order to obtain better tuning. It will be seen that 

 with this arrangement of transmitting and receiving 

 stations there are four distinct circuits, two at each 

 station, which have all to be in tune. Using this system 

 Mr. JNIarconi has been able to attain very satisfactory 



NO. 1649, VOL. 64] 



syntony even although the same vertical wire be used 

 for the different sets of signalling apparatus, which would 

 be connected to it, in such a case, through inductances 

 of different values. 



A still further improvement is effected by combining 

 the two methods described above ; in this case the con- 

 nections are made as shown in Fig. 4, which does not 

 require any further explanation, 



Mr. Marconi concluded his lecture with an account of 

 some of the achievements already made with wireless 

 telegraphy. The development has been so rapid under 

 his able guidance that one feels that almost as one 

 writes the systems being described are becoming out of 

 date. Perhaps before long Mr. Marconi will have 

 succeeded, by the use of suitable mirrors and lenses, in 

 guiding the radiation in a definite direction, and thus 



Fig. 4. 



have effected a great gain in efficiency. But whether 

 this should prove practicable or not. Air. Marconi is to 

 be congratulated on the brilliant success of his efforts, 

 and deserves the gratitude of all for having worked out 

 so admirable a system for increasing the safety and con- 

 venience of those "that go down to the sea in ships, 

 that do business in great waters." 



THE ANTARCTIC EXPEDITION. 



TO our great regret the officers of the Royal Society 

 have not yet, so far as we know, made any state- 

 ment regarding the hopeless condition of aftairs which 

 has arisen in relation to the Antarctic E.\pedition in 

 consequence of the recent action of the Council. 



It will be of interest to our readers to observe, in the 

 paragraph we quote below, from Science of May 24, the 

 manner in which the management of the Antarctic Ex- 

 pedition is regarded by the scientific men of another 



