"The power of arbitrarily dismissing those in one's employ, is a power exercised in a great degree over a vast number of persons in this country, without their having any redress at law. Put the case of a day labourer or ordinary servant. You may refuse to give him a character, and he has no redress. If you give him a false character, he has the means of redress, but that is of a very different kind. And this is the law of the land."