I have been impressed for some time with the unsatisfactory character of the present fog signals. We must recognize that powerful siren signals are sometimes inaudible at distances but little exceeding a mile. It is true that these worst cases of inaudibility may not recur during fogs—as to this there seems to be insufficient evidence. But even when a sound-in-air signal is audible, the information conveyed is far from precise. The bearing of the source cannot be told with much accuracy, indeed some say that it cannot be told at all. The distance is still more uncertain. I should say that no system is satisfactory which does not give either the one or the other element, bearing or distance.

The system of synchronous signalling explained by Prof. Joly claims to give the distance with sufficient precision, and the American and Russian trials show that the claim is justified, as might indeed have been expected with some confidence, provided both signals themselves are well defined in time. The wireless electric signals are easily made sharp. Submarine signals from a bell, or explosive, would also be sharp enough. So probably would be explosive signals in air. The case of siren signals is more doubtful. Possibly the end might be sharp enough. Even so, the objection of the uncertain carrying of air signals remains.

I do not know whether there is already sufficient experience of submarine signals. If it be true that they can be depended upon up to distances of at least 4 or 5 miles, the case is strong for a combination of them with electric signals.