Dr Davy on Atmospheric Electricity. 441 



well secured, a glass tube, to which was attached, and by means 

 of which was insulated, a copper wire of moderate thickness, fur- 

 nished with short projecting lengths of fine wire of pure gold. 

 This upper conductor thus terminating, stood about six feet 

 above the summit of the turret. For communication with the 

 earth, another copper wire was used, the inferior end of which 

 was immersed in water contained in a small cistern, from whence 

 a leaden pipe descended through the building to the ground. 



On the 13th of last October I began the experiments, and 

 continued them till the middle of March, when I was obliged to 

 stop, in consequence of having to prepare to leave Malta and re- 

 turn to England. 



The first experiment instituted was on the gelatinous trans- 

 parent compound, formed by mixing together moist starch and a 

 strong solution of the iodide of potassium, which is, I believe, 

 the most delicate of all the tests yet known of electro-chemical ac- 

 tion. The two conductors were connected with naked platina 

 wires, which passed through a cork into a glass tube containing 

 the compound in which they were plunged, about a quarter of an 

 inch asunder. The results of this experiment were clear and de- 

 cisive. I shall limit myself to mentioning them briefly. In fine 

 weather, even when the sky was cloudless, a slight precipitation 

 of iodine was commonly observed, in the course of twenty-four 

 hours, on the platina wire of the inferior conductor. When the 

 wind was strong, the effect was occasionally greater ; and it was 

 almost invariably so when clouds were passing, especially low 

 clouds. The direction of the wind did not appear to influence 

 the effect materially ; on the whole, ceteris paribus, perhaps the 

 effect was more marked when the south-east wind, the damp 

 sirocco, was blowing, than when the cooler and commonly drier 

 north-west wind prevailed. These remarks apply to dry wea- 

 ther, at least to absence of rain. During thunder storms, and 

 during showers of hail even without thunder, and heavy showers 

 of rain, the effect was more strongly marked. In the two first 



