or the particular rate of combustion desired. The
draft required for various kinds of fuel is treated in detail in the
chapter on "Chimneys and Draft". In this chapter it will be assumed that
the draft is at all times ample and that it is regulated to give the
best results for each kind of coal.

TABLE 40

ANTHRACITE COAL SIZES

_________________________________________________________________
| | | |
| | | Testing Segments |
| | Round Mesh | Standard Square |
| | | Mesh |
| Trade Name |__________________|__________________|
| | | | | |
| | Through | Over | Through | Over |
| | Inches | Inches | Inches | Inches |
|___________________________|_________|________|_________|________|
| | | | | |
| Broken | 4-1/2 | 3-1/4 | 4 | 2-3/4 |
| Egg | 3-1/4 | 2-3/8 | 2-3/4 | 2 |
| Stove | 2-3/8 | 1-5/8 | 2 | 1-3/8 |
| Chestnut | 1-5/8 | 7/8 | 1-3/8 | 3/4 |
| Pea | 7/8 | 5/8 | 3/4 | 1/2 |
| No. 1 Buckwheat | 5/8 | 3/8 | 1/2 | 1/4 |
| No. 2 Buckwheat or Rice | 3/8 | 3/16 | 1/4 | 1/8 |
| No. 3 Buckwheat or Barley | 3/16 | 3/32 | 1/8 | 1/16 |
|___________________________|_________|________|_________|________|

Anthracite--Anthracite coal is ordinarily marketed under the names and
sizes given in Table 40.

The larger sizes of anthracite are rarely used for commercial steam
generating purposes as the demand for domestic use now limits the
supply. In commercial plants the sizes generally found are Nos. 1, 2 and
3 buckwheat. In some plants where the finer sizes are used, a small
percentage of bituminous coal, say, 10 per cent, is sometimes mixed with
the anthracite and beneficial results secured both in economy and
capacity.

Anthracite coal should be fired evenly, in small quantities and at
frequent intervals. If this method is not followed, dead spots will
appear in the fire, and if the fire gets too irregula