592 REPOET— 1888. 



there was drawn up a code of rules for the guidance of tbose who erected these 

 conductors. He might say that that report itself was most decisive and it was 

 most important. He could not help reading out to them, because it would form 

 the basis of a good deal that would be said that day, how they defined a lightning- 

 conductor : — ' A lightning-conductor fulfils two functions. It facilitates the dis- 

 charge of the electricity to the earth, so as to carry it off harmlessly, and it tends 

 to prevent disruptive discharge by silently neutralising the conditions which 

 determine such discharges in the neighbourhood of the conductor. To effect the 

 first object a lightning-conductor should offer a line of discharge more nearly 

 perfect and more accessible than any other offered by the materials or contents of 

 the edifice we wish to protect. To effect the second object the conductor should be 

 surmounted by a point or points ; fine points and ilames have the property of 

 slowly and silently dissipating the electrical charges ; they in fact act as safety- 

 valves. If all those conditions be fulfilled, if the points be high enough to be the 

 most salient features of the building, no matter from what direction the storm- 

 cloud may come, be of ample dimensions and in thoroughly perfect electrical 

 connection with the earth, the edifice with all that it contains will be safe, and the 

 conductor might even be surrounded by gunpowder in the heaviest storm without 

 risk of danger. All accidents may be said to be due to a neglect of these simple 

 elementary principles. The most frequent sources of failure are conductors deficient 

 either in number, height, or conductivity, bad points or bad earth connections.' 

 The paragraph ended with this most decisive and clear assertion, an assertion that 

 he was there to defend, and that was that there was ' no authentic case on record 

 where a properly constructed conductor failed to do its duty.' 



Now here they had defined the functions of a conductor, and lest it should be 

 thought that they neglected the teachings of modern theorists he thought it was 

 only right to point out that they asserted in the Report of the Lightning-rod Con- 

 ference, * We will assume the conductivity of equal lengths and weights of iron in 

 the case of steady currents of electricity ' ; and further on they asserted ' that the 

 suddenness of lightning discharge modifies the conductivity.' Now that report, he 

 might say, was signed by Professor Grylls Adams, Professor Ayr ton, Latimer Clark, 

 E. E. Dymond, Carey Forster, D. E. Hughes, Peter Lewis, W. H. Preece, G. J. Symons 

 and John Wychgrove. He had a great deal of experience in the performance of 

 lightning-protectors. He personally had under his supervision at that present 

 moment 500,000 lightning-conductors, and fixed throughout the offices of this 

 country they had their apparatus protected by about 30,000 or 40,000 lightning- 

 protectors. Professor Oliver Lodge was selected to deliver lectures at the Society 

 of Arts. If all the vaticinations of Oliver Lodge were true, the work of this Com- 

 mittee and the work of the last 140 years would be useless ; no lightning-protector 

 could possibly protect and no discharge could possibly be led to earth. 



Now those were strong assertions. He thought that Professor Oliver Lodge 

 had in his papers before the Society of Arts, and in his paper published in the 

 ' Phil. Mag.,' committed certain fallacies that it was now his (Mr. Preece's) duty to 

 bring before them. Now in the first place Professor Lodge assured them that a 

 lightning-rod formed a part of a flash. Well it did not. Nobody had ever 

 seen, to his knowledge, a flash of lightning strike a conductor. The function of a 

 lightning-conductor was to prevent the possibility of its being struck by a flash, and 

 if it were struck by an infinitesimal part of a flash, then he said that lightning-pro- 

 tector was not a lightning-protector : it bad some defect in its construction that had to 

 be remedied. But suppose it did. Then the lightning-protector would form but a 

 very small portion indeed of the path of the lightning discharge from the cloud to the 

 earth. A great deal depended upon the height of the thunder clouds. They saw in 

 text-books ridiculous assertions about the length of lightning flashes. Well, now, 

 who could measure the length of a lightning flash ? There had been several extremely 

 accurate measurements of the height of thunder clouds. In South Africa Dr. Mann 

 measured, and his measurements made the height 650 feet. But the most accurate 

 mea.surements had been made by M. Lacoiu, a Frenchman in charge of the Otto- 

 man telegraphs in Constantinople, and there he made the height of a cloud, there- 

 fore the length of a flash, about 325 feet. Well, they had those two measurements, 



