As hail is only produced in summer, and is always attended with storms, some philosophers have believed that the sudden departure of electricity from a cloud may effect something yet unknown in this phenomenon; but it may happen in summer independent of electricity, because the aqueous vapour is then raised higher in the atmosphere, whence it has further to fall, and there is warmer air below for it to fall through.] [_Or sink in silver dews_. l. 18. During the coldness of the night the moisture before dissolved in the air is gradually precipitated, and as it subsides adheres to the bodies it falls upon. Where the attraction of the body to the particles of water is greater than the attractions of those particles to each other, it becomes spread upon their surface, or slides down them in actual contact; as on the broad parts of the blades of moist grass: where the attraction of the surface to the water is less than the attraction of the particles of water to each other, the dew stands in drops; as on the points and edges of grass or gorse, where the surface presented to the drop being small it attracts it so little as but just to support it without much changing its globular form: where there is no attraction between the vegetable surface and the dew drops, as on cabbage leaves, the drop does not come into contact with the leaf, but hangs over it repelled, and retains it natural form, composed of the attraction and pressure of its own parts, and thence looks like quicksilver, reflecting light from both its surfaces. Nor is this owing to any oiliness of the leaf, but simply to the polish of its surface, as a light needle may be laid on water in the same manner without touching it; for as the attractive powers of polished surfaces are greater when in actual contact, so the repulsive power is greater before contact.] [_The blue mist_. l. 20. Mists are clouds resting on the ground, they generally come on at the beginning of night, and either fill the moist vallies, or hang on the summits of hills, according to the degree of moisture previously dissolved, and the eduction of heat from them. The air over rivers during the warmth of the day suspends much moisture, and as the changeful surface of rivers occasions them to cool sooner than the land at the approach of evening, mists are most frequently seen to begin over rivers, and to spread themselves over moist grounds, and fill the vallies, while the mists on the tops of mountains are more properly clouds, condensed by the coldness of their situation.