608 EEPORT — 1888. 



performed in a much smaller way, and more resembling the conditions which 

 existed in an actual phenomenon. Suppose instead of usmg those two condensers 

 they used the two poles of the Holtz machine, or instead of having two pairs of knobs 

 suppose they used only one pair of knobs. They might connect the poles of the Holtz 

 machine, if they pleased, with a large battery of Leyden jars, and they would get 

 all the better eil'ect. The arrangement then was that they got a spark between the 

 two knobs of the Holtz machine. They connected that by an alternative path and 

 then they tested to see at what distance it was just possible for a spark to take place. 

 He wanted to ask Professor Lodge when that experiment was being performed 

 whether an iron alternative path or a copper alternative path was the better. The 

 circumstances seemed to him to more resemble the circumstances in nature than 

 the arrangement which he had described in his experiment ; and he thought the 

 conclusion was that the copper alternative path was the better, which would be an 

 argument in favour of Mr. Preece's view. 



Sir James Douglass said the few remarks that he had to make upon this 

 matter were in relation to his experience with a large number of conductors in 

 exposed stations now extending over about forty years. He might say that his 

 experience was comforting to the Committee. His experience was with lighthouse 

 towers ; and there they had been following out for nearly the last fifty years the 

 advice of Faraday entirely. For protecting a lighthouse he advised them to start 

 with the base of a metallic lantern. The conductors were of an inch and a half by 

 three-quarters half round ; that was to say, the half of an inch-and-a-half copper 

 bar ; they were carried down the interior of the tower, on the internal walls of the 

 tower, with branches from all metal work in the tower. The earth was obtained 

 by a copper plate 2 feet 6 inches square, buried at a distance of 15 feet from the 

 tower and about 12 feet from the surface, generally securing damp contact. 

 At exposed stations at sea the bar was carried down to about 8 or 10 feet below 

 low-water spring tides so as to be always immersed in the wave. He might 

 say that during forty years perhaps seven or eight accidents had occurred, but 

 no accidents of a serious nature : and in all cases when an accident had occurred 

 they had been able to discover that it was due to a defect in the conductor. 

 Generally it had been found due to a mechanic who had been about the station 

 who had disconnected the conductor and had not properly connected it again. 

 Therefore those were points which he felt confident were to be got over by 

 more rigid inspection, and more rigid inspection was now being carried out. He 

 for one would feel that he would be perfectly safe in any tower where this system 

 was carried out, and where the conductors were properly looked after. Having 

 them carried down in the interior of the building they had every opportunity 

 of inspecting them, and he rarely visited a lighthouse but what he inspected every 

 connection up and down, and generally tested the conductor with a common lines- 

 man's instrument from top to bottom. 



There was one practical point on the question of iron versus copper, and it was 

 this, the rapid corrosion of iron compared with copper. It was quite possible 

 with an iron conductor in an exposed station, where they were subject to such a 

 corrosion, no matter v/hat their sectional area might be, if they visited that station 

 in the course of seven or eight years they would find very little of that conductor 

 left. He had known bars of large diameter corroding at the most rapid rate 

 possible in this country, and of course it was much more rapid in hotter climates. 

 He only introduced that as a considerable fact of experience with conductors in 

 (xposed stations. 



There was one point that he had omitted to mention, and it was comforting to 

 Mr. Preece that during forty years where those conductors had been carried out on 

 towers in contact with dwellings only one case of accident had occurred to sur- 

 roundino- dwellings, and there it was due to the imperfection of the conductor in 

 the tower. The mischief was caused to the dwelling by the imperfection of the 

 conductor in 1he tower; it was not a case of the dwelling being struck from the 

 outside. 



Mr. Stdh^ey Walkek, speaking from the point of view of the practical en- 

 gineer, said : — Upon the question of iron or copper for practical purposes, he should 



