254 



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



as that of " brittle " zinc, and the lines of fracture ran across the crys- 

 tals revealed on the changed surface in such a way as to show that 

 these crystals seen on the surface are not a thin superficial layer, but 

 genuinely represent the entire structure of the metal. 



I am therefore led to the conclusion that the action is simply one of 

 recrystallisation. The metal in the state in which it reaches us in foil 

 or crucibles, &c, is in a condition of severe strain, having been bent, 

 drawn, rolled, &c, either in the cold or at temperatures far below its 

 " annealing " temperature. This is supported by the fact that the 

 platinum in its " unchanged " state shows a very minute structure 

 characteristic of severely strained metals. The natural effect of expo- 

 sure to a high temperature of metal in such a condition is to allow it 

 to recrystallise, and this I conceive to be what occurs in the case of 

 platinum. The brittleness of the " annealed " metal is not at all sur- 

 prising, as the same phenomenon occurs with zinc and cadmium (see 

 paper cited above). In the case of platinum " annealed " in a gas flame 

 there is, however, a further action ; simple annealing or recrystallisa- 

 tion, although it will completely alter the interior structure of a piece 

 of metal, will not of itself alter the appearance of the surface even in 

 microscopic detail. To develop a surface pattern corresponding to the 

 changed internal structure the surface must be etched after the recrys- 

 tallisation has taken place. The etching action is in this case un- 

 doubtedly due to the gases of the flame, and the temporary formation 

 of a carbide may play a part in this process. 



" On some Phenomena affecting the Transmission of Electric 

 Waves over the Surface of the Sea and Earth." By Captain 

 H. B. Jackson, RE, E.B.S. Eeceived May 1,— Bead 

 May 15, 1902. 



In 1895, systematic experiments were commenced by me with a 

 view of utilising the effect of Hertzian waves on imperfect electrical 

 contacts, for naval signalling purposes. 



I soon observed that some unexpected phenomena were deterrent 

 factors in obtaining the necessary accuracy at all times, and with the 

 most modern and improved instruments that we now possess, this is 

 equally noticeable. 



The results of some of the phenomena are described in this paper,, 

 with the conclusions that I have drawn as to their cause. 



Some of the experiments described were specially conducted with 

 the object of elucidating definite results on the subject. Other experi- 

 ments carried out with a different object, and also ordinary practical 

 signalling at various times, also gave the results described, without in 



