John Locke, "Considerations, etc., in relation to money" (published in 1691), says:
The greater scarcity of money enhances its price and increases the scramble; there being nothing that does supply the want of it; the lessening of its quantity, therefore, always increases its price and makes an equal portion of it exchange for a greater of any other thing.
Prof. Francis A. Walker, "Money," etc., page 210, says:
Gold and silver do, over long periods, undergo great changes of value and become in a high degree deceptive as a measure of the obligation of the debtor of the claim of the creditor. Thus Professor Jevons estimates that the value of gold fell between 1789 and 1809, 46 per cent., that from 1809 to 1849 it rose 145 per cent., while in twenty years after 1849 it fell again at least 20 per cent.
Jevons, "Money and Exchange," chapter 6, says:
In respect to steadiness of value the metals are probably less satisfactory, regarded as a standard of value, than many other commodities, such as corn.
And again, in chapter 24 of the same work, he says:
We are too much accustomed to look upon the value of gold as a fixed datum line in commerce; but in reality it is a very variable thing.
Sir Archibald Alison (England, in 1815 and 1845), says:
The coining of gold and silver, which is universal in all civilised nations, and affixing to them one definite and permanent value by authority of law, has no effect whatever in preventing the fluctuations in the real value of the current coin of the realm.