In process of time, and as people became gradually more familiar with the use of the different metals in coin, and consequently better acquainted with the proportion between their respective values, it has, in most countries, I believe, been found convenient to ascertain this proportion, and to declare by a public law, that a guinea, for example, of such a weight and fineness, should exchange for one and twenty shillings, or be a legal tender for a debt of that amount.