Fractional coins are those of smaller denominations than the standard unit of money, as shillings and pence in England, and half dollars, quarter dollars, dimes, nickels, and cents in America.  Money to serve well a variety of uses must be of different denominations, and “small change” is necessary to make small purchases and for exact settlement in larger payments that are not multiples of the standard unit.  The amount required (or most convenient to use) in each denomination of fractional coins is thus a more or less certain portion of each person’s monetary demand, shaped by experience and fixed by habit.  For example, within certain elastic limits of convenience quarters may be used for halves, and dimes for nickels (and vice versa); but each person has a point of preference.  The total demand for each kind of change is the sum of the individual demands.  This point where the amount of coins of any denomination (in relation to the whole monetary system) is most convenient may be called the saturation point of that kind of small change, up to which point the people prefer a share of their money in that form, and beyond which they will, if free to choose, exchange that kind for other denominations (smaller or larger).  Each kind of money, as the cent, nickel, dime, has its own peculiar demand and its saturation point.

MONETARY SYSTEM OF THE UNITED STATES, 1915

Metals | Weight, grains | Fineness |Ratio to gold
1.  Gold coins | 25.8 | .90 | 100
2.  Silver dollar | 412.5 | .90 | 15.988 to 1
3.  Silver, subsidiary | 385.8 | .90 | 14.953 to 1
4.  Nickel (5 cents) | 77.0 | .25 | ...........
5.  Copper (1 cent) | 48.0 | .95 | ...........
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Metal |Limit of issue | Legal tender for|Receivable for
| | private debts |public dues
1.  Gold coins | Unlimited. | Unlimited. |For all
2.  Silver dollar |Ceased in 1905 | Unlimited. |For all
3.  Silver, | Needs of the | $10 |$10
subsidiary | people | |
4.  Nickel (5 cts.) | Do. | 25 cts. |25 cts.
5.  Copper (1 ct.) | Do. | 25 cts. |25 cts.
| \ |
Paper | | |
6.  Gold certificates|Unlimited in ex-| No |For all
|change for gold | |
7.  Silver |In exchange for | No |For all
certificates | silver $ | |
8.  US notes | No new issues. |Unlimited. |Except customs
9.  Treasury notes | No new issues. |Unlimited |For all
of 1890 | | |
10.  National bank |Capital of banks|No |Except customs