TKAKSACTIONS OF SECTION A. 607 



M. DE FoNViELLE (wbo spoke in French) said he was sorry that he Lad the 

 honour to be called upon to give his opiuion on that occasion, as he arrived in the 

 room late, but he would try to glance at some of the speeches that he had heard from 

 so many distinguished electricians. Sir William Thomson said most eloquently that 

 Mr. Preece was taking the English side of the question, and Mr. Lodge the Ameri- 

 can side, but he must say that Sir William Thomson had taken the French side and 

 had proposed a revolutionary system which consisted in the building of ii"on 

 houses. He took the liberty, though a Frenchman, to disagree with the great 

 electrician and to stand with his friend Mr. Preece as an English Conservative of 

 lightning-conductors. Lord Rayleigh said that mathematicians and physicists should 

 unite together, hut he supposed that he would agree with him in remarlring that 

 Mr. Preece was realising that alliance in a very remarkable manner, as on the one 

 band he was dealing with a large number of experiments and observations of 

 nature, and on the other his application of statistics, or rather his calculation of 

 probabilities, belonged to one of the highest branches of mathematics. The experi- 

 ments done in laboratories differed from those which were presented bv nature in 

 regard to their size. On the previous day in that very hall his friend M. Janssen 

 had proved by his observations on the action of oxygen on light that in many 

 phenomena there was a coefficient behind varying according to the square or higher 

 power. They might suppose that in electricity the law might relate accordingly to 

 some unknown power, so they must wait for observations of natural phenomena 

 from the clouds. They were so much more bound to wait because photography 

 was now coming to their help, and it was impossible to say what were the powers 

 he referred to until they had seen what photography coidd do. He would advise 

 the meeting to delay its opinion until the time when his countrymen had erected 

 in Paris the Eiffel Tower, which would be the most extraordinary lightning-con- 

 ductor in existence, being a thousand feet high, and which would supply unpi-ece- 

 dented means for observation and experiments. He must, moreover, state that 

 Paris was practically free from calamities produced by lightning because they had 

 a sufficient number of lightning-rods erected according to the principles so admir- 

 ably advocated by Mr. Preece. That was strong evidence that Mr. Preece was 

 in the right direction, altogether irrespective of any mathematical or physical 

 question. 



Professor George Foebes said: — Let them keep before their minds in this discus- 

 sion what the question was which they wished to determine. The question had 

 arisen from Mr. Lodge having come with those experiments to prove that the 

 views of the Committee on Lightning-rods were erroneous. The Committee on 

 Lightning-rods had come to a definite conclusion to make a recommendation that 

 copper should be used for the lightning-rods, and Dr. Lodge had come to say that 

 if iron was not better it certainly was as good ; and that was the question which had 

 to be decided. Now Professor Rowland had already said that it was not quite 

 certain that the experiments which Dr. Lodge had brought forward were perfectly 

 conclusive on this point. No one could fail to be enormously impressed with the 

 beauty and the value of those experiments from a scientific point of view ; but he 

 thought that it was quite a fair position for Mr. Preece to take up to say that at 

 present they had not proved the fact that the conclusions of the Committee on Light- 

 ning-rods ought to be given up. He would illustrate what he meant in this way. 

 They had heard once of Professor Lodge's experiments veiy clearly put before them 

 in which they had an alternative path either of copper or of iron. Previous to 

 those experiments most persons would have expected that the copper would have 

 been a better conductor for the alternative path. Professor Lodge assured them as 

 the result of his experiments that copper was not the better hut was probably the 

 worse of the two. 



Now he wished to show them the reason why he thought they were not 

 fully able to accept that experiment as sufficing to abolish copper rods for their 

 lightning-condvictors. It was this. In the experiment Professor Lodge had used two 

 condensers, and he had used a special case in which there were two sparks pro- 

 duced beside the alternative path. He asked Professor Lodge to tell them what 

 was the result. He had doubtless tried the experiment when the experiment was 



