DISCOVERY 



73 



in Russia one receives about 240,000 roubles to the 

 pound. 



After my experience of the terrible scenes which I 

 have described, and others, more terrible, which are 

 beyond description, I returned by various methods to 

 Pinsk, whence I took train to Warsaw. On this line 

 one train a day runs in each direction, the journey of 

 approximately 300 miles taking twenty hours. This 

 is due partly to the fact that the railway stock is in a 

 very poor condition, and partly to the fact that the 

 track is so bad that high speed would be dangerous. 

 The chief cause of the length of the journey, however, 

 is the fact that the train invariably stops for periods 

 of from half an hour to two hours at intermediate 

 stations. The reason for this I was unable to ascertain. 

 All the information I could gather was that there was 

 no hurry, and that to-morrow would do as well as 

 to-day. 



During the days I was in Warsaw, the rate of ex- 

 change was as bad as 12,730 marks to the English pound. 

 It afterwards fell to 20,000, and then rose again to 

 about 12,000. To the Pole 10,000 marks represent 

 £500 in pre-war figures, and though, of course, it has 

 not that value at the present time, it is nevertheless a 

 very large sum. 



Altogether, though prices are high according to 

 the Polish idea, Warsaw itself wears an air of something 

 akin to prosperity, though the condition of the roads 

 is appalling. 



Wireless Navigation and 

 Nocturnal Flight 



A French scientist's solution of the problem 

 of aerial nocturnal flight and the 

 guidance of vessels into port by means 

 of a Cable-guide and Wireless 



By George Frederic Lees 



The problem of aerial flight by night or in foggy weather 

 — one of the most difficult problems with which avia- 

 tion experts have been faced — is now within sight of 

 solution, thanks to a development of wireless tele- 

 graphy imagined and applied, first of all in the case of 

 ships at sea and afterwards in the case of aeroplanes, 

 by a young French scientist, Monsieur W. A. Loth, 

 who until recently was a student, under the late 

 Monsieur Boutroux, at the Fondation Thiers, Paris. 

 The Academy of Sciences has already recognised the 

 value of M. Loth's maritime work by bestowing upon 

 him its " Prix de Navigation." Recently a practical 



demonstration of the great utility of the invention 

 was given by M. Loth on the aviation ground of the 

 Nieuport Company at Villacoublay, near Paris, and 

 many experts who gathered there considered the 

 experiments very striking. 



Since this new departure in aeronautic science is 

 based on M. Loth's first invention, that of the cable- 

 guide for ships entering difficult harbours, it will be 

 well if I begin with a short account of this electrical 

 discovery, which is already being exploited commer- 

 cially. For the harbours of Brest and Le Havre are 

 about to be supplied with cable-guides ; a project is on 

 foot to lay one of these cables between another French 

 port and one of the south coast ports of England ; 

 whilst applications for similar installations are coming 

 from maritime authorities in many parts of the world, 

 notably Belgium and South America. 



In considering the means by which a vessel navigates 

 into port at night-time, M. Loth soon came to the 

 conclusion that visual signals are useless in foggy 

 weather, that sounds, such as foghorns which are used 

 in practice, are uncertain, and that plotting one's 

 position from wireless signals affords a series of approxi- 

 mate points only. In brief, the navigator is at the 

 mercy of many errors. But, if the entrance to a given 

 port were supplied with a submerged cable and the 

 navigator could be furnished with a means of following 

 it, it is evident that the problem might be solved. 

 So the inventor set to work to find a way of locating 

 such an invisible cable. After experiments had been 

 made on a small scale on the Seine with a motor- 

 launch and a cable lying on the bed of the river, 

 M. Loth transferred his operations, under the auspices 

 of the French Admiralty, to Brest, where a properly 

 insulated and protected cable was laid. On land, in 

 the port, he placed a source of electric current, an alter- 

 nator, and connected one pole of the generator to the 

 copper core of the cable, the other to a plate immersed 

 in the sea. Now, during an alternation an electric 

 current flowed through the cable, and the end of the 

 cable being bare the current returned through the sea 

 to the copper plate connected with the other pole of 

 the alternator. In the next alternation a similar 

 circuit was traversed in the reverse direction. Such 

 was the principle. All that remained to be done was 

 to locate the current flowing through the cable, and 

 this, M. Loth found, could be done in several ways. 

 The method finally adopted will now be described. 



Four receiving spirals are installed on board the 

 vessel. These spirals are constructed of a number of 

 turns of wire wound on wooden frames forming boxes, 

 the frames being strongly built and well insulated. 



Two are large (with sixty turns), one being arranged 

 transversely, the other longitudinally with respect to 

 the ship ; two are small (ten turns), one placed trans- 



