264 Capt. H. B. Jackson. On some Phenomena [May 1, 



made by her at the rate of twenty-five per minute by my syntonic 

 transmitter. 



The results showed that the signals ceased and commenced abruptly 

 at the moment that the aerial wire passed the tangent from the trans- 

 mitting ship to the edge of the cliff ; the action was so abrupt, that, on 

 one transit, the latter part of the long sign in the " F " was the first 

 indication of signals that was received ; and on another transit, in the 

 opposite direction, the long of the "F" was the last sign received, 

 the short being dropped ; these were unusual results, as the signals 

 generally die away gradually, the long signs breaking up, thus : 



( ), and the shorts appearing as clots (.), before any signs are 



actually lost. 



Another point that may now be considered, is the case shown in 

 fig. 4cb, when signals could not be exchanged when the ship was close 

 under the land, but could be when clear of the land and in the same 

 direction as before; the trial was repeated on several occasions for 

 verification. 



Possibly the case previously considered, fig. 6, is of the same class, 

 as it is noteworthy, that when the ship was further off the promontory 

 and also from the transmitting ship, though the two ships were still 

 masked by high land of much greater thickness than before, a few 

 stray signals were received occasionally, which evidently passed over, 

 not round, and not through the land, as the ship was then in a land- 

 locked bay. 



Eeferring now to figs. 3e and 3/, where the intervening land was 

 both higher and thicker, and yet did not stop signals at longer propor- 

 tional distances, it may be concluded that the waves of electrical 

 induction, which must pass from ship to ship in order to record signals, 

 may in certain cases pass through the land. Fig. 2 is a good example 

 of this : one of the ships was lying alongside a perpendicular cliff of 

 considerable height, and yet only experienced a loss of distance of 

 about 12 per cent. 



Fig. 8a gives a typical case of waves passing through valleys, and 

 the results were so marked and so frequently repeated with different 

 ships and on separate occasions that eventually the track of a vessel, 

 proceeding at a known speed, could be roughly estimated, though 

 distant 25 miles, by noting the intervals between the times when 

 signals were lost and when received, and comparing these intervals 

 with the time taken by the ship to cover the distances between the 

 valleys, which were well delineated on the chart, and through which 

 the waves could evidently wind their way with less obstruction than 

 by any other route. 



We have thus obtained evidence that the waves of electric induction 

 may pass (1) through land, (2) over land, (3) round land, but that a 

 large proportion of their energy is lost in doing so. (4) That the 



