602 EEPORT— 1888. 



the summer, he believed, when the lightning clouds were high, and they got very 

 little damage done ; on the contrary, in winter time the thunderstorm clouds were 

 very low, and the churches were very frequently struck. That, he thought, was 

 all that he need say. 



Lord Ratleigh said he had no special experience whatever of lightning-con- 

 ductors, and could only speak from a general knowledge of electricity, no doubt to 

 be applied in this case to very peculiar circumstances, so that everything that stood 

 upon a merely « priori foundation should be put forward with very great diffidence. 

 He must say, however, tliat Professor Lodge's experiments had seemed to him to 

 be likely to have most important practical applications to lishtning-conductors. 

 He could not see how experiments dealing with the thing of all others most 

 like lightning that could be produced in the laboratory could fail to have such 

 an application. Professor Lodge aslied one question and he thought mentioned 

 his (Lord Rayleigh's) name in connection with it, as to how it could happen 

 that an oscillatory electric current, that was, say, an alternate electric cur- 

 rent beginning at a finite magnitude and gradually dying away, could produce 

 magnetising effects such as they well knew tliat in some cases it did ; and he in- 

 stanced the very opposite behaviour, of slowly dying away alternating currents in 

 the experiments of Professor Ewing and of others, in which such an arrangement 

 was precisely the one adopted in order to get rid of even the last traces of 

 magnetism. The question was a difficult one certainly, and be had intended iu 

 fact to make some experiments upon it himself; but he was inclined to think that 

 the explanation might perhaps be sought in a case very much akin to the one 

 with which tbey were now dealing, namely, that of the magnetic steel needle which 

 was magnetised, say, by the discharge of a Leyden jar flowing through a spiral in- 

 volving the needle. He said the needle itself was a conductor of finite dimensions, 

 and that during the very rapid passage, and he had no doubt iu some cases 

 alternations of electric current through the spiral, there were induced in the magnet 

 itself, in the steel needle itself, which ultimately became a magnet, circumferential 

 currents, which circumferential currents would first, at any rate, protect the interior 

 of the iron from the direct magnetising action of the enveloping helix. They must think 

 not only of the action of the oscillating current in the helix upon the various parts 

 of the steel needle, but also of the action of the currents developed in the steel 

 needle itself. He believed it had been well ascertained that at different depths in 

 such a steel needle they would very often find different degrees and even different 

 directions of magnetisation. It seemed to him possibly that if that was thoroughly 

 followed out the)' would be better able to understand what was certainly the fact, 

 that a current that was certainly alternating and gradually dying away did never- 

 theless produce and leave behind it the effect of strong magnetisation. 



There was only one other point that had occurred to him which it would be 

 necessary to mention in connection with the development of atmospheric electricity, 

 and he would like very much to hear any meteorologists present express their 

 views upon it. He was reading only the other day a pamphlet by Professor 

 Swankey, a man who had done very good work in other departments of science, 

 in which he developed the theory that atmospheric electricity was due to the 

 friction between water and ice. There was no doubt that many clouds (cirrous 

 clouds he believed nearly always) were ice clouds, and not water clouds. Dr. 

 Swankey 's view was that at a certain level iu the atmosphere ice clouds and water 

 clouds could meet ; and that under those circumstances this friction might occur : 

 and his view was that the atmospheric electricity was the result of such friction. 

 He quoted experiments by Fai-aday on the friction of ice and water, which had a 

 positive result. But that was, perhaps, not the main question before them. He 

 would rather hear from some more experienced and practical men, who had been 

 at work on lightning-conductors especially, any instances of the kind that 

 Professor Lodge asked for of actual failures of lightning-conductors. It seemed 

 to him that it was only by actual experience of the lightning-conductors that the 

 question could ever be finally settled. The laboratory experiments might be most 

 important as suggestions, but he thought no one would wish finally to adopt any 



