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 
