152 ANNUAL OF SCIENTIFIC DISCOVERY. 



NEW LIGHTNING CONDUCTOR. 



At a recent meeting of the Franklin Institute, Mr. J. D. Rice presented a 

 new design for Lightning Conductors. The conductor is formed of fluted 

 tubes of copper, joined by screw sockets, the ends of the tubes abutting, so 

 that the communication is complete. The top is terminated, as in the most 

 approved plans, with a single upright piatina point, surrounded by radiat- 

 ing pointed copper wires, set at an angle with a vertical line. The object 

 of the corrugations is, to present a greater surface in a less diameter, and to 

 stiffen the material ; they also give the conductor an ornamental appearance, 

 which the generality of them do not possess. 



THEORY OF THE VOLTAIC TILE. 



During the thirty years in which the theory of the pile has been under dis- 

 cussion, research has favored apparently at one time the chemical, and at 

 another the contact theory. We are able now, as we believe, to announce 

 that the discussion is closed. The chemical theory has definitely triumphed. 

 As explained in the Traite d'Electricite The'orique et Pratique of De la 

 Rive, this theory meets all difficulties and proves that if contact is often 

 necessary for exciting electricity, it is not that which produces it ; chemical 

 actions are always the source. This learned physicist demonstrates that 

 all chemical action causes a disengagement of electricity, whilst not a 

 single experiment can be cited in which electricity is produced simply by 

 contact. 



He reviews and explains all the alleged facts in favor of the theory of 

 contact. He thus shows up the objection so often urged, that in order to 

 displace by iron the copper of the sulphate of copper it is necessary to put 

 the iron in contact with the saline solution, and that the chemical action 

 begins only after the iron is covered with copper and when it has thus 

 formed a voltaic couple. De la Rive first proves that in this experiment 

 there is a voltaic couple which precedes that formed by the iron and by the 

 displaced copper ; this couple is formed by the iron and the oxide of iron ad- 

 hering to its surface or by iron and carbon or some other foreign body ; for 

 by using iron chemically pure and a surface perfectly clean, no precipitation 

 of copper is obtained. 



No physicist is better fitted than De la Rive to undertake the delicate task 

 of giving a theory of the pile. His studies as well as his discoveries lead 

 him in this direction. 



De la Rive was the first who recognized the important fact that zinc 

 chemically pure is not attacked by hydrated sulphuric acid ; that two metals 

 on which pure nitric acid, for example, has no action, such as gold or plat- 

 inum, give not the slightest trace of a current when put to the extremity of 

 a galvanometer and plunged into the nitric acid ; that on the contrary, they 

 produce an instantaneous current when a drop of chlorohydric acid is added. 

 The theory of contact has never yet explained this fact. Silliman's Journal. 



