B. TERRESTRIAL PHYSICS AND METEOROLOGY. HI 



January, a wet April, or a dry June, will either of them 

 give a bad crop in the harvest of that same year; while the 

 chances are about two to one that a wet August, a dry July, 

 a dry December, a dry September, or a wet October, will be 

 followed, either of them, by a bad crop in the following 

 year. 



The influence of these unfavorable circumstances in pro- 

 ducing bad crops will amount to about thirteen per cent, 

 of the whole crop. 



LIGHTNING AND LIGIITNING-CONDUCTOES. 



The new Society of Telegraph Engineers has discussed 

 with much fullness, in several of its public sessions, the sub- 

 ject of lightning and lightning-conductors. Mr. Preece, the 

 secretary of the society, considers the subject as aflecting the 

 interest of telegraphy, and also the safety of vessels and 

 houses. The direct eflect of lightning on the telegraph wires 

 seems to be not so serious as its indirect effect in inducing 

 ground currents. From a correspondence between Faraday 

 and Latimer Clark, it seems that the long under-ground cir- 

 cuits between London and Manchester suffered considerable 

 derangement from these induced currents. Usually, when 

 lightning strikes telegraph poles, they are completely de- 

 stroyed, unless the stroke divide itself among several poles. 

 As regards the protection of ships from lightning, Preece 

 conceives that accidents from this cause have almost entirely 

 disappeared. Such vessels as have been damaged are inva- 

 riably those that have been unprotected. The heavy cost 

 of the system used for ships has probably had a serious influ- 

 ence in checking the employment of a similar system to pro- 

 tect buildings ; but Preece endeavors to show that it is pos- 

 sible for a man to render his house absolutely as safe as a 

 ship at an expense w^hich may be considered trifling. A 

 chimney lined with a thick layer of soot, by which a current 

 of heated air is ascending, is an excellent but a dangerous 

 conductor ; hence so many indoor accidents. The conditions 

 that determine a perfect lightning-conductor are that it shall 

 expose in some prominent position on a building a metallic 

 point, and that it shall ofter from this point to the earth a 

 path of little or no resistance to the passage of the current. 

 Preece contends that, instead of the costly copper rods, the 



