378 WRITINGS OF JOSEPH HENRY. [1855- 



the company was obliged to take them up and repair the 

 damage to prevent the loss of gas. An occurrence of this 

 kind might perhaps lead the proprietors of gas-works to ob- 

 ject to the proposition of connecting the end of the rod with 

 their mains ; but they should recollect that if means be not 

 furnished to prevent the danger consequent upon the use of 

 gas, a less amount of the article will be consumed ; and fur- 

 thermore that giving more efficiency to the inductive action 

 of the rod on the cloud by the connection we have pro- 

 posed, the tendency to a discharge will be lessened ; and 

 finally, that if the connection be not formed, the discharge 

 from the cloud will itself find the main through the gas- 

 pipes within the house. 



There is another source of danger of a similar character 

 in cities supplied with water from an aqueduct; the pipes in 

 different stories of the buildings, connected with the water 

 mains which under-lie the city, in most intimate connection 

 with the earth, are subject to a powerful induction from the 

 cloud above, and therefore will attract any discharge which 

 may be passing in their vicinity, or even determine the 

 point at which the rupture of the stratum of air between the 

 cloud and the house shall take place. In this case the light- 

 ning-rod should also be connected with the pipes under 

 ground, in order that the induction through the rod should 

 be as perfect as possible, and that the consequent attraction 

 may confine the charge and transmit it entirely to the largo 

 mains, and from them to the earth. Houses are sometimes 

 supplied with water from the roof, collected in tanks in the 

 loft, whence it is distributed by pipes to different parts of 

 the building. This arrangement also tends to invite the 

 lightning in proportion to the perpendicular elevation of 

 this system of conductors. The lower ends of these are not 

 usually in very intimate connection with the earth, and 

 therefore a less powerful induction takes place than in the 

 other instances we have mentioned. They should however 

 be placed as in the preceding case in good metallic connec- 

 tion with the lightning-rod on the outside of the house. 

 The same remark applies to steam and hot-water pipes used 

 for heating large buildings. 



