350 Proceedings of the Eoyal Society of Edinburgh. [Sess. 
therefore a vessel comes into the neighbourhood or over the top of the wire^ 
those on board can detect its presence, and in consequence can locate their 
position. The currents have, if desired, different characteristics just as light- 
house apparatus has.” 
In virtue of what has now been stated the Council of the Royal Society 
of Edinburgh claim that the method of the pilot cable, tacitly credited to 
M. Loth, is essentially the same as that first described by Mr C. A. Steven- 
son and published in their Proceedings in 1893. It seems to be a simple 
act of justice that these historical facts should be clearly recognised, and 
that due credit should be given to Mr Stevenson for his valuable pioneer 
work in the interests of humanity. The system of the pilot cable is, in 
fact, Mr Stevenson’s system. Compared with M. Loth’s beautiful devices 
made possible in these days by the remarkable developments in methods 
for detecting electric and magnetic changes, Mr Stevenson’s early methods 
may appear crude : but that does not invalidate his claim as the originator 
-and the first experimenter along these lines. Not only did he invent the 
pilot cable, but he was the first to demonstrate practically how it could be 
used in guiding vessels up estuaries and into harbours by means of electric 
signals from a sunk cable. 
C. G. Knott, 
General Seeretary, R.S.E. 
A French translation of this statement was sent in the hope that it 
might find a place in the Comptes Rendus. The following reply was 
received from M. Picard. 
“ Institut de France, 
“ Academie des Sciences, Paris, 
“ Juin 26, 1922. 
“ M. Emile Picard, Secretaire Perpetuel de TAcademie des Sciences, a 
M. C. G. Knott, Secretaire general de la Societe Royale d’Edimbourg. 
“ Monsieur le Secretaire general, 
“ J’ai bhonneur de vous transmettre la lettre que m’a ecrite M. lAmiral 
Fournier a la suite de votre communication relative an prix attribue a 
M. Loth par TAcademie des Sciences de Paris. J’y joins deux numeros de la 
Revue generate PEledricite et du Genie civile contenant des articles se 
rapportant a la question du guidage des navires. II resulte de ces divers 
documents que le probleme pratique de guider un navires restait entier apres 
les interessantes communications de M. Stevenson dormant seulement un 
principe general qui parait d’ailleurs avoir ete anterieurement indique. On 
doit reconn aitre, avec M. TAmiral Fournier, que le precede d’emission et 
Tappareillage de detection decrit par M. Stevenson dans son brevet et dans 
la note de Proceedings ne permettaient pas de guider avec securite les navires 
-entrant dans un port ou en sortant. Or cela seul est interessant pour la 
