The small bubbles are oxygen, and their smallness is due to the perfect cleanness of the surface on which they are liberated.

The hydrogen adhering to the other electrode swells into large bubbles, which rise in much slower succession; but when the current is reversed, the hydrogen is liberated upon the cleansed wire, and then its bubbles also become small.
Footnotes to Chapter 5 [1] Buff finds the quantity of electricity associated with one milligramme of hydrogen in water to be equal to 45,480 charges of a Leyden jar, with a height of 480 millimetres, and a diameter of 160 millimetres.

Weber and Kohlrausch have calculated that, if the quantity of electricity associated with one milligramme of hydrogen in water were diffused over a cloud at a height of 1000 metres above the earth, it would exert upon an equal quantity of the opposite electricity at the earth's surface an attractive force of 2,268,000 kilogrammes.

(Electrolytische Maasbestimmungen, 1856, p.

262.) [2] Faraday, sa Vie et ses Travaux, p.