76 



On Lightning Rods. 



Vol. III. 



distance above the ground, should be made 

 of largfer iron, to enable it the better to with- 

 stand the corroding effects of rust. Several 

 feet of the top of the rod should be drawn out 

 by a regular taper to suit the size of the point. 

 It also renders the top of the rod lighter and 

 more steady. 



As the delicate point of an iron rod would 

 be speedily destroyed by rust, it become.s 

 necessary to employ some metal for the point, 

 which is not liable to corrosion. Platina and 

 goid are most commonly used ; and good 

 points may be purchased ready made ; but 

 the value of these metals renders them objec- 

 tionable. Either they do not contain enough 

 of the precious stuff, or the expense is too 

 great. The comparative cheapness of silver 

 allows us to use it in larger quantity, and it 

 is equally well suited to the purpose. An 

 ordinary blacksmith can make two good silver 

 points out of a half dollar, and save sufficient 

 stuff to pay him for his labor. It should first 

 be cut as marked in fig. 16, and the larger 



Fig. 16. 



pieces forged into points, either square or 

 round, about two or three inches long, with 

 a top to screw into a hole drilled in the top 

 of the rod. — See fig. 17. It may be proper 



Fig. 17. 



in thi'^ place to correct a very common error, 

 that brightness is essential to a good point. 

 Brightness is only necds.'sary a.s a security 

 for sharpness. The brightness is do.^trnyfd 

 by rust, and rust destroys the point. The 

 sharper it is the better it will operate. 



The rod should be planted yn deep as In 

 insure its connexion with moist earth, even 

 during the dryest seasons. Dry earth is a 

 non-conductor of electricity ; hence, if it be- 

 comes dry about the foot of the rod, the pass- 

 age of the fluid from the cloud to the earth 

 becomes interrupted, and the rod rendered 

 useless. To insure a more perfect connexion 

 ■with the ground, I would advise to dig a hole 

 eeveral feet deep, according to the situation, 

 whether dry or moist. An old stove plate or 

 other iron casting, should be laid in the bot- 

 tom for the rod to stand on, and tico or three 

 bushels of charcoal placed in the hole before 

 the earth is filled in. The iron enlarges the 

 surface of contact between the rod and earth, 

 and the charcoal, having a strong affinity for 

 water, will retain moisture better than the 



clay. The rod should be so bent about the 

 surface of the ground, that the foot may stand 

 off from the building at a considerable angle. 



The manner of attaching the rod to the 

 building, deserves some care. If it performs 

 its office well, and prevents the stroke, this 

 is of no consequence. But if, from any cause, 

 the lightning should strike the rod, a metal 

 fastening might conduct it into the wall, espe- 

 cially where the connexion with the ground 

 was imperfect. When iron hooks or staples 

 are u.^ed, it is a common practice to enclose 

 the rod, where it passes through them, in 

 some non-conducting substance, such as the 

 neck of a porter bottle, or a piece of horn 

 or bone. Equal or greater security may 

 generally be obtained by passing the rod 

 through blocks of wood, and nailing them to 

 the wall ; dry wood being also a non-con- 

 ductor. A etill better plan, where it can be 

 done, is to attach the rod to a pole, and ele- 

 vate it along side of, or near to the building. 



The length of the rod should always be 

 such as to elevate its point as far as possible 

 above the top of the building, and every con- 

 tiguous object. This should be carefully 

 attended to, for it is found that all objects, 

 such as chimneys, trees, &c. when near to 

 the point, diminish its effects in a rapidly in- 

 creasing ratio to their height, until they ren- 

 der it entirely useless. Thus the rod attached 

 to the low building, in fig. 18, being com- 



pletely overtopped by the higher one, is ren- 

 dered incapable of affording any protection to 

 either of thrtu, while a proper nxJ attached 

 to the higher building, would effectually 

 guard them both against danger. 



We too often see conductors hang dangling 

 by the sid.'' of buildings, with the lower end 

 broken off; or only imperfectly connected 

 with the ground. Still more frequently we 

 see the point scarce'y raised above the top 

 of the building, or completely overhung with 

 trees. The protection which they aflord must 

 be very precarious. Indeed, we often hear 

 of Buch buildings, or rods, or the overhanging 



