Mobile register and journal., 1845-02-08

ful explosions and loss of life have ensued large quantity of gunpowder, belonging to the Republic of Venice, had heen deposited in the vaults oi the church of St. Nazaire al Brescia The tower of the church struck with lightning in August, l767; the elec- fic fluid descended the vaults and exploded above POI 500 pounds oi gunpowder. About three thousand persons perished hy this catastrophe, and nearly sixth of the fine cliy of Brescia was destroyed. Ow- ing to the same wani of protection. a magazine Df 400 barrels of gunpowder blown up Tn Sumatra, in l7S2, " an electrical discharge; and at Lnxem- burg, in 1907, magazine with twelve tons of gun. powder exploded by lightning, and the lower part of the town laId in ruins.
 But while facts such as these indicated the value of thunder rods cases frequently occurred where the ihuntlerholt fell upon objecIs in low situations, while the higher objects in their immediate vicinity were spared; and in such il also inferred that the theory of conductors was in fault, M Achard, in MemoIr read 10 the Academy of Sc ence at Ber lin, mentioned two of this kind In one of them, the two objects were equally good conductors of electricity. In the other the elevated object which escaped was the tower of church surnouHed by weathercock of iron; while the object which the lightning struck was cottage very near the lower without any iron ils ioo and haiched with straw. Rut though cases of this kind which M. Achard fesses himself unable reconcile with the heory of conductors, prevented their general introduction, il dues in our own day, yet m almost all the larger cities of Europe and America, ihnnder.rods gradually employed for the protection o powder mag | | We have previously treated of the statistics and | ph osophy of storms, and have described many of the prnrinal electrical phenomena which accompany them In the Barhaloes hurricane of the 18th and and l9ih August, 1881, these phenomena were | awfnit grand n their nature, and new and inex- pcable in ihe character, that it would be desirable study the electrical separately from the mechanical | phenomena uf such hurricanes, and endeavor to ob- tain surh general explanation of lhem. The meleors and lightning which accompany the gales of the East | and West Indies have been overlooked amid the ap- pang dangers of the tempest, and in very few of | ihe Maurus gales, except in that of the Boyne in 1885, have the eectrical phenomena heen all ub- served So trivial, indeed, is the part which thun- der and lightning plsys in these tremendous convui. snns of nalure that al Mpniego Bay, in the hurri- cane of the 8rd October, l7S0, when an earthquake added its awful con ngent to the general horrors of the scene, the prodgious flashes of lightning, which followed in regular secession, regarded, not as a source of danger hui as a real blessing, amid the | midnight darkness which brooded the general | desnlation.'
 Our limits will rot allow us to pursue this inter- | estng subject furter; and must, therefore, de- vote our few remaining pages to brief notice of the best method of prOectng our buildings from light ming, and of Mir. hrris's system of conductors for | ships.
 Were our houses powder magazines, and ships, built of iron, dO they consist of framework of iron, fl led up with sone, brTk, or wood, they might bid defiance 10 the ayages of accidental or wlul hre, as well as all tle lightning of the tropics Strike where il might, the deadly fluid woui be conducted quietly to the gr"uid. Ip the time, however, we must have recoirse to n less perfect system of protection, till advancing know ledge and receding prejudice shall have introduced iron buidings and
 iron ships. as we'll iron ploughs. iron roads, and iron bridges.
 Al the conductive powers of lead, fin, iron, zinc, aud copper, areas the Nos. I-2-24 4--4 and l2, copper is the bes material for conducting rods The quantity of meta in the rod should not he less than what IS rontained" cylinder half meh in diam eier. II iron is ued, the c, Hinder should be nearly an inch and two enths in diameter. The metallic rod should be hatened rather than round, SO as to have he gr,atesl surface that is consistent with strength. The conductor thus formed should commit nicaie with all the detached masses of metal in he building, such le,den ridges, gutters, and metallic pipes. It should le attached tO the most elevated point of the building and if the structure to con- sist of numerous rages, such the Houses of Parliament, long pointed rods should project from the most prominent lars into he atmosphere. In place Of adopting the usual method of external conductors, shoud commend the introduction of vertical iron bar ito the thickness of the principal walls of the building These bars should communi- cate with horzont,l wall plate of iron uniting the whole; and from this wall plate should rise all the external conductors which to project into the at- mosphere