146 Miscellaneous Intelligence. 



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 

 witli great care. Copper or brass wire is, however, 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 

 toof, 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 light" 

 ning 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. 



Paratonnerres for Churches, 



For a tower, the stem of the paratonnerre should rise from 15 to 

 24 feet, according to its area; the domes and steeples of churches, 

 being usually much higher than the surrounding objects, do not 

 require so high a conductor as buildings with extensive flat roofs. 

 For the former, therefore, their 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. 



Paratonnerres for Powder-'Magazines, 



These require to be constructed with the greatest care. They 

 should not be placed on the buildings, but on poles at from six 

 to ten feet distance. The stems should be about seven feet long, 

 and the poles of such a height, that the stem may rise from 15 to 

 20 feet above the top of the building. It is also advisable to 

 have several paratonnerres round each magazine. If the maga- 

 zine be in a tower, or other very lofty building, it may be suf- 

 ficient to defend it by a double copper conductor, without any 

 paratonnerre stem. As the influence of this conductor will not 

 extend beyond the building, it cannot attract the lightning from 

 a distance, and will yet protect the magazine, should it be struck. 



Paratonnerres for Ships, 



The stem of a paratonnerre for a ship, consists merely of a copper 

 point, screwed on a round iron rod, entering the extremity of the 

 top-gallant mast. An iron bar, connected with the foot of the 

 round rod, descends down the pole, and is terminated by a crook 

 or ring, to which the conductor of the paratonnerre is attached, 

 which, in this case, is formed of a metallic rope, connected at its 

 lower extremity with a bar or plate of metal, and which latter is 

 connected to the copper sheathing on the bottom of the vessel. 



