A NAME for the unit coefficient of self-induction is much wanted. No one is satisfied with secohm, and yet it seems making its way; by reason, no doubt, of Ayrton and Perry's ingenious commutating arrangement for helping to measure it. It is an unpleasing name, and it is too big a unit. The name quad, which I formerly suggested, is on further consideration still less satisfactory for permanent use, because it emphasizes unduly the accident that in electro-magnetic measure self-induction happens to be a length. One looks forward to the time when all distinction between electrostatic and electro-magnetic measures shall vanish by both ceasing to be; and at that not far-distant time, names emphasizing the present arbitrary state of things will be anachronisms, as well as stumbling-blocks to beginners. I beg to suggest that a milli secohm shall be called a vo. It is a short and harmless unmeaning syllable not yet appropriated. It should be its own plural. The unit of conductivity is already styled a mo; and 8 vo will look well alongside 12 mo. “Vo-meter” is short and satisfactory. A unit of magnetic induction will then be the vo-ampere; and this, being of a size convenient for dynamo makers, may be hoped to replace their abominable mongrel unit “Kapp-lines.”