1824.] Conductors of Lightning. 435 



gutters made to discharge their water over it, so as to keep it 

 always moist. Too great precautions cannot be taken to give 

 the lightning a ready passage into the ground, for it is chiefly 

 on this that the efficacy of a paratonnerre depends. 



As iron bars are difficult to bend according to the projections 

 of a building, it has been proposed to substitute metallic ropes 

 in their stead. Fifteen iron wires are twisted together to form 

 one strand, and four of these form a rope, about an inch in 

 diameter. To prevent its rusting, each strand is well tarred 

 separately, and after they are twisted together, the whole rope 

 is tarred over again with great care. It is attached to the stem 

 of the paratonnerre in the same manner as the bar-iron conduc- 

 tor, by means of the collar B, fig. 15, the ears of which, in this 

 case, are made rather concave in order better to embrace the 

 rope. Instead of a fork, the stanchions which support it over 

 the roof, are terminated by a ring, O, fig. 12, through which the 

 rope passes. At about six feet deep in the ground, it is united 

 to an iron bar, about three-fourths of an inch square, in which 

 the conductor terminates as seen at C, fig. lb', for the rope 

 would soon be destroyed in the ground. Bars of iron, however, 

 are preferable to the rope, but if, from peculiarity of situation, 

 it be absolutely necessary to adopt them, copper or brass wire is 

 a better material for their construction than iron. 



If a building contain any large masses of metal, as sheets of 

 copper or lead on the roof, metal pipes and gutters, iron braces, 

 &c. they must all be connected with the paratonnerre, by iron 

 bars of about half an inch square, or something less. Without 

 this precaution, the lightning might strike from the conductor to 

 the metal (especially if there should be any accidental break in 

 the former), and occasion very serious injury to the building, 

 and danger to its inhabitants. 



o 



Paratonnerres for Churches. 



For a tower the stem of the paratonnerre should rise from 

 about 15 to 24 feet, according to its area; the domes and 

 steeples of churches, being usually much higher than the sur- 

 rounding objects, do not require so high a conductor as build- 

 ings with extensive flat roofs. For the former, therefore, thin 

 stems, rising from three to six feet above the cross or weather- 

 cock, will be sufficient, and being light they may easily be fixed 

 to them, without injuring their appearance, or interfering with 

 the motion of the vane. 



When difficult to fix, the stem of a paratonnerre for such 

 buildings may even be omitted altogether, and merely the foot 

 of the cross or weathercock be well connected with the ground. 

 This arrangement requires little expense, and is well adapted for 

 country churches. Fig. 23 represents a steeple without any 

 stem to the paratonnerre, its cross being connected with the 



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