There is an implied contract, much stronger than any instrument or
article of agreement between the labourer in any occupation and his
employer--that the labour, so far as that labour is concerned, shall
be sufficient to pay to the employer a profit on his capital, and a
compensation for his risk; in a word, that the labour shall produce an
advantage equal to the payment. Whatever is above that, is a direct
TAX; and if the amount of that tax be left to the will and pleasure of
another, it is an ARBITRARY TAX.