NATURAL PHILOSOPHY 



OX THE CONSTRUCTION OF THE TERMINATIONS OF LIGHTNING- 

 CONDUCTORS. 



AT a recent meeting of the Scottish Society of Arts, an animated discussion 

 took place in reference to the construction of the terminations of lightning-- 

 conductors one party maintaining that the present pointed terminations 

 were theoretically and practically wrong, and that balls, or knobs, should be 

 substituted, and the other that the electricity was best discharged by pointed 

 conductors. The arguments in favor of the use of balls instead of points 

 were given by Mr. Hepburn, who stated " that he had been led to doubt the 

 efficiency of the conductors usually adopted, terminating in points, which was 

 contrary to the plan found to be necessary in the management of artificial 

 electricity, in which, while the fluid is gradually collected from the excited 

 cylinder by a row of pointed wires attached to the prime conductor, its trans- 

 mission from the conductor to the battery, and the discharge of the battery 

 itself, is always effected by balls. It thus appears that for the absorption and 

 transmission of an accumulated mass of electricity an extended surface is re- 

 quired ; and as in the protection of buildings it is necessary to provide for the 

 instantaneous absorption of a concentrated mass of electricity darting through 

 the air in the form of a flash or ball, Mr. Hepburn conceived that the con- 

 ductor ought te terminate hi one or more pear-shaped balls, having a surface 

 sufficient to absorb at least as much of the fluid as the descending rod is 

 capable of carrying to the earth. It remains to be determined whether a 

 large hollow ball, or a smaller solid one is preferable." 



STRINGFELLOW S POCKET ELECTRIC BATTERY. 



This is an ingenious arrangement for supplying a continuous stream of elec- 

 tric fluid for medical purposes, and it especially recommends itself by its 

 extreme portability, and by the convenient manner hi which it can be applied. 

 A battery of sufficient power for most purposes is contained in a holder no 

 larger than a lady's card-case, and it owes its comparative compactness to 

 contrivances by which an immense number of minute surfaces of suitable 

 metals are arranged so as to induce the voltaic action. The novelty of the 

 arrangement consists in the repetition of a peculiarly constructed element, , 

 which is made as follows : A narrow strip of thin zinc is bound round with a 



