820 THE POPULAR SCIENCE MONTHLY. 



ground. But the conductor provided by the electrical engineer acts 

 in precisely the same way, and with equal efficiency, in either case. It 

 provides the means by which the electrical disturbance may set itself 

 at rest in a quiet and unexplosive way. The chief danger that has to 

 be feared is the purely economical one that there is always a tendency 

 on the part of the imperfectly informed public to limit too narrowly 

 the cost, and in that way to impair the efficacy, of the engineer's work. 

 The duty of the engineer is, summarily, to see that his building is ade- 

 quately covered above by the lines of the conducting network, that 

 the main channel of his conductor is ample for any storm overflow that 

 it can, by any possibility, be called upon to accommodate, and that 

 the outlet to the earth is capacious and free. Even in the present state 

 of electrical science it can, with the utmost confidence, be affirmed, 

 not only that wherever destructive accidents have occurred in associa- 

 tion with lightning-conductors, such accidents have, in every case, been 

 due to the circumstance that the conductors have been of faulty con- 

 struction, but also that in by far the greater number of instances the 

 fault has been in the least conspicuous and least obvious part of the 

 apparatus, where the earth contact has to be established. In his report 

 on the lightning-conductors of the Paris International Exhibition, Pro- 

 fessor Rousseau states that it is in this particular that lightning-rods 

 most generally and most flagrantly fail. In one passage of the report 

 he says : 



I do not know whether I have defined with sufficient precision what is im- 

 plied in*a good communication with the earth, but I think the principle, at any 

 rate, may be laid down that the communication of a lightning-conductor with 

 the earth can not be considered good if it is inferior to that of any masses of 

 metal that lie in its close neighborhood. If this is the case,- it may be antici- 

 pated, as has so frequently been found, that the lightning will quit the paraton- 

 nerre to pass to the object which is in better communication with the earth. It 

 is thus that buildings have been frequently set fire to by hghtning which has 

 leaped from paratonnerres to gas-pipes. In one notable case, after striking the 

 conductor of a church in New Haven, United States, the lightning left the con- 

 ductor to pierce a brick wall fifty centimetres (nearly twenty inches) thick, to 

 get at a gas-pipe which rose twenty feet out of the ground a little distance off. 



We ourselves some little time ago investigated the nature of an ac- 

 cident occasioned by lightning, which so strikingly confirms the views 

 expressed by Professor Rousseau that it is worthy of being specifically 

 brought under notice here. In the year 1865 the tower of the church 

 of All Saints, in Nottingham, was struck by lightning during a severe 

 thunder-storm. The tower was one hundred and fifty feet high, and 

 had a small rope of copper wire, intended to serve as a lightning-con- 

 ductor, descending along its west face from one of its comer pinna- 

 cles to the ground, where the rope terminated by being coiled round a 

 stone buried, a few inches in the dry soil. On the inner face of the 

 same wall of the tower, near its base, and only separated from the con- 



