TRANSACTIONS OF SECTION G. 871 



metal strip emploj'ecl, and the character of the section. The strips are rolled 

 between a series of molettes, which produce the reijuisite corrugation, much on 

 the same principle that the larger sections in iron and other metals are rolled in 

 the mill. IJecentl}', by an improvement in the processes of manufacture, it has 

 become possible to produce a flexible pipe in which the coils are soldered together 

 or otherwise united by a tight joint, as the tube is formed, and the flexibility is 

 obtained by the extension and compression of V-shaped folds in the metal. Statis- 

 tics are given of the strength of various tubes, m.any of the smaller sections having 

 withstood strains amounting to 2,000 lb. per square inch, and some account follows 

 of the industrial applications of flexible tubing and the numerous purposes in the 

 arts for which this invention may be applicable. 



SATUIIBAY, AUGUST C. 

 The Section did not meet. 



MOXDAY, AUGUST 9. 



The following Papers were read : — 



1. Jie;port on Graphic Methods. By Professor H. S. Hele Shaw.^ 



See Reports, p. 373. 



2. The Destruction of Lightning Protectors by recent Ilunieipal Legislation. 



By W. H. Preece, F.lt.S. 



The immunity of private houses from being struck by lightning is very marked, 

 and this is considered to be due to the fact that the lead on our roofs and the iron 

 stack-pipes that drain these roofs, connected as they are together, ibrm admirable 

 lightning protectors. Any chare'e of atmospheric electricity which may fall upon 

 a house so protected is conveyed harmlessly away to the earth. Householders are 

 now required to remove these pipes from direct connection with the drains, and to 

 leave an air space between the end of the pipe and the grating of the drain. The 

 result is that the electric conduction of the pipe is broken, the stack-pipe ceases to 

 be a lightning protector, and houses are left exposed to the dangers of atmospheric 

 electricity. 



The remedy is very simple. The pipe need not be entirely cut away ; three- 

 fourths of its circular section may be removed for the distance required, and one- 

 fourth may be left to maintain the old electrical connection, or if the separation 

 has been effected, then the stack-pipe should be connected with the drain by a 

 wire or rod so as to restore a path for the charge to the earth. 



Householders are also now compelled to put up stack-pipes to ventilate their 

 soil-pipes, erecting above their roofs a metal tube Ibrming a prominent object, 

 exposed to the atmospheric charge, and terminating frequently in an earthenware 

 pipe on the first floor. They are thus liable to be struck by lightning without 

 ofl'ering any means of escape. They should be connected electrically with the 

 earth, either directly or indirectly, through the stack-pipes, which would then 

 make them sources of safety rather than of danger. 



' Ordered to be printed in extcmo. 



