by Dr. Van Marum. 319 



through which the (hock paffed. The fame effects 'were pro- 

 duced in warm-blooded animals, for example rabbits, with 

 much (mailer batteries. Now, as, in confcquencc of fuch de- 

 rangcmcp.L, circulation of the blood can no longer take place, 

 this circumftance, without all doubt, is the caufe of the 

 fudden death of thofe ftruck with lightning. Ifthefhock 

 does not pafs through the large arteries the animal may ftill 

 recover, provided the cerebellum and fpinal marrow be not 

 injured. 



19. The effetls of fuch flocks from a battery on trees. — 

 Nairne, in the year 1773, niaae experiments of this kind on 

 different plants, particularly myrtles and laurels. Dr. Van 

 Marum, for his experiments, made choice of much more 

 vigorous trees, fuch, for example, as the young (terns of a 

 common willow-tree, and at a period, viz. the middle of 

 April, when the young branches ufually (hoot forth. 

 Through two of thefe, eight feet in length, he conveyed 

 (hocks, the firft through a fpace 15 inches in length, and 

 two others through their top. After the experiments- thefe 

 trees were planted ; but the parts through which the (hocks 

 had been conveyed fent forth no branches. The upper parts 

 through which tie (hocks had palled, fent forth a few (hoot* 

 for fome days, but very (lowly, and which foon after died. 

 Thofe not electrified fent out branches like the other trees 

 planted near them. The effects of electricity, therefore, are 

 iimilar to thofe of lightning. 



20. Experiments on co/nhtclors. — Dr. Van Marum had 

 concluded from his former experiments that a rod of lead 

 mu ft be four times as large in diameter as one of iron to 

 withttand lightning in the fame maimer. Thefe dimenfions, 

 however, arc fufficient for the ftrongeft lightning. It ap- 

 peared alfo that copper conductors are equal to thofe made of 

 iron, even when their diameter is only one-half of that of 

 iron ones. This appealed alfo from Brooks's experiments, 

 who concluded that a flip of lead four inches in breadth, and 

 fo thick that a fquare foot of it amounts to eight pounds, 

 cannot be hurt by lightning. The experiments made by 

 means of the large battery refpecYmg the conducting pro- 

 perty of copper, gave very different refults. As an iron wire 



T t ? « of 



