EXPERIMENT STATION BULLETINS. 199 



necting it to the nearest rain-water pipe. The resistance of a tubular 

 earth on this plan g»hould be very low and practically constant. 



27. Inspection. — Before giving his final certificate the architect 

 should have the conductor satisfactorily examined and tested by a 

 qualified person, as injury to it often occurs up to the latest period of 

 the works from accidental causes, and often from carelessness of work- 

 men. 



28. Inspection may be considered under two heads: 



A. The conductor itself. 



B. The earth connection. 



A. Joints in a series of conductors should be as few as possible. As 

 a rule they should only be necessary where the vertical and horizontal 

 conductors are connected, and the main conductors themselves should 

 always be continuous and without artificial joints. Connections between 

 the vertical and horizontal conductors should always be in places readily 

 accessible for inspection. Visible continuity suffices for the remainder 

 of the circuit. The electrical testing of the whole circuit is difficult and 

 needless. 



B. The electrical testing of the earth can in simple cases be readily 

 effected. In complex cases, where conductors are very numerous, tests 

 can be effected by the provision of test clamps of a suitable design. 



29. Collieries. — Undoubted evidence exists of the explosion of fire- 

 damp in collieries through sparks from atmospheric electricity being 

 led into the mine by the wire ropes of the shaft and the iron rails of 

 the galleries. Hence the head gear of all shafts should be protected 

 by proper lightning conductors. 



SUGGESTIONS OF THE COMMITTEE. 



The investigations of the committee warrant them in jjutting forward 

 the following practical suggestions* 



1. Two main lightning rods, one on each side, should be provided, 

 extending from the top of each tower, spire, or high chimney stack by 

 the most direct course to earth. 



2. Horizontal conductors should connect all the vertical rods (a) 

 along the ridge, or any other suitable position on the roof; (?>) at or near 

 the ground. 



3. The upper horizontal conductor should be fitted with aigrettes 

 or points at intervals of 20 or 30 feet. 



4. Short vertical rods should be erected along minor pinnacles and 

 connected with the upper horizontal conductor. 



5. All roof metals, such as finials, ridging, rain-water, and ventilating 

 pipes, metal cowls, lead flashing, gutters, etc., should be connected to 

 the horizontal conductors. 



6. All large masses of metal in the building should be connected to 

 earth either directly or by means of the lower horizontal conductor. 



7. Where roofs are partially or wholly metal lined, they should be 

 connected to earth by means of vertical rods at several points. 



8. Gas pipes should be kept as far away as possible from the positions 

 occupied by lightning conductors, and as an additional protection the 

 service mains to the gas meter should be metallically connected with 

 house services leading from the meter." 



