1882.] QUESTION BOS. 223 



melted the wire, was an illustration. There are cases on rec- 

 ord where an iron rod, three-quarters of an inch in diameter, 

 has been heated red hot ; but such cases are exceedingly rare. 

 I dare say that in the case Mr. Sedgwick mentioned there was 

 an exceedingly strong discharge, and his rod was not large 

 enough to carry the electricity all off. 



Mr. Augur. I would like to ask Prof. Brewer if the light- 

 ning-rods which are made and offered to the public at present 

 are any of them sufficient, or as they should be ? 



Prof. Brewer. I cannot answer that question, whether 

 any of them are. I know that a good many are not. It is 

 possible that some of them are. It is not true that surface 

 makes any difference. We get two things mixed. When 

 electricity is still upon the conductor of an electrical macbine, 

 it is only on the surface ; but when in motion it moves 

 tlirough the whole mass. The amount of electricity conveyed 

 througb a rod has nothing to do with its surface. If you take 

 a wire and roll it out flat as a ribbon, it will convey no more 

 and no less electricity than tlie round wire. The electricity 

 that is collected in a Leyden jar, for instance, is only upon 

 the surface ; but when it moves, like the electricity that is 

 used in conveying messages by the telephone, or any form of 

 electric apparatus where the electricity is in motion, or in a 

 lightning-rod, it moves through the mass, and the laiger the 

 conducting mass the more easily it moves. As a consequence, 

 an iron ship, or an iron car, or even a car upon a railroad 

 with a large amount of iron about it, is never injured by light- 

 ning. Take it on the western plains, where emigrant-wagons 

 have been repeatedly struck. I dare say many of yuu have 

 seen emigrant-wagons having lightning-rods attached to them. 

 There is no case on record where a railroad-car has been 

 struck, and the reason is, that there is a very large amount 

 of metallic surface, and a great iron rail underneath the car 

 to carry off the electricity. 



Question. Will scions taken from a tree bearing odd 

 years, when grown upon another stock, follow the habit of 

 bearing the odd year ? 



