Prof. De la Rive 07i Electrieiiy. 267 



terminate in a point of copper, gilt, or platina. The conduc 

 tors ought to be either iron-bars of seven or eight square lines, 

 or iron-wire of the same diameter. These conductors should 

 be solidly fixed, by a metaUic joining, to the vertical rod, and 

 this again should descend into a well, if there be one' in the 

 neighbourhood, so as to plunge 2 feet at least into the water; 

 and if there be no wells, then they ought to be buried in a hole 

 10 or 15 feet deep, and surrounded with coal-coom, which has 

 the double advantage of facilitating the flow of the electric 

 fluid, and of preserving the iron from rust. When the edifice 

 is large, and it is deemed necessary to have more than one con- 

 ductor, it is advantageous they should all communicate with one 

 another by means of iron -bars, thus uniting them into a com- 

 plete whole. There is, moreover, in the memoir, many valuable 

 hints concerning the construction of the several pieces of conduct- 

 ing apparatus, and also of the most eligible method of arranging 

 them, answering to the plan of the building to be protected. 

 Thus it is said, that, in the case of steeples surmounted by a 

 cross, it is sufficient to establish a communication betwixt the 

 cross and the earth, by a good conductor, to preserve both the 

 steeple and the neighbouring building. We may here add, 

 though there is nothing said of it in the memoir, that experience 

 has proved, that those mansions the roof of which are tolerably 

 covered with white iron, communicating with the earth by means 

 of metallic water-pipes, are, by these means, well sheltered from 

 the lightning, and may be considered as protected. 



We would here add a word on the electricity developed by the 

 Torpedo. Since Sir H. Davy's investigations on the subject, 

 unequivocal signs of electrical currents have been obtained by 

 touching certain points of the body of the animals with the two 

 extremities of the galvanometer. At the recommendation of the 

 illustrious chemist, these researches were undertaken by his bro- 

 ther Dr Davy, who, whilst in Malta, could easily procure the liv- 

 ing animals. By applying the extremities of the metallic wire 

 of the galvanometer to the two extremities of the electrical or- 

 gan, there was established in the wire a current capable not only 

 of affecting the needle, but also of strongly magnetizing needles 

 that before were not magnetized ; this current could also decom- 

 pose a saline solution, and produce shocks ; but the author could 

 not succeed in discovering sensible traces of heat or of light. 



