C = the circumference of the wheel in inches.
The formula is expressed verbally as follows: Double the stroke and multiply it by the total steam pressure on both pistons; divide the product by the circumference of the driving-wheel in inches.
ADHESION.
313. As observed on page [307], the adhesion or the bite of the wheels upon the rail is, as an average, from one fifth to one sixth of the weight; one fifth when the rail is in a good state, and less when wet or greasy; we cannot depend upon more than one sixth in practice. Therefore, if the tractive power of an engine is 3,000 lbs. we must, to make it available, place 3,000 × 6 or 18,000 lbs. upon those wheels which are connected with the machinery, (driving wheels).
FUEL.
314. The fuels employed in the locomotive engine for the evaporation of water are wood, coal, and coke. In England the latter is used exclusively. In America the first has, on account of its cheapness, been quite generally adopted; but of late railroad companies have been turning their attention to coal and coke.
The immense beds of coal distributed throughout the United States will furnish fuel to railroad companies almost without limit. Its position as well as its amount will render its adoption practicable in nearly all of the States. Ohio alone contains more coal than all of Great Britain. The following table is from the iron manufacture of Frederick Overman.
| Name of State. | Area of Coal-fields. | |
|---|---|---|
| Georgia | 150 | square miles. |
| Maryland | 550 | square miles. |
| Alabama | 3,400 | square miles. |
| Tennessee | 4,300 | square miles. |
| Michigan | 5,000 | square miles. |
| Missouri | 6,000 | square miles. |
| Indiana | 7,700 | square miles. |
| Ohio | 11,900 | square miles. |
| Kentucky | 13,500 | square miles. |
| Pennsylvania | 15,437 | square miles. |
| Virginia | 21,195 | square miles. |
| Illinois | 44,000 | square miles. |
| In all | 133,132 | square miles. |
315. The following table (also from the works of Overman) gives the nature and evaporative power of the different American coals.
| Name of Coal. | State where found. | Percentage of carbon. | Steam of 212° evaporated per lb. | Quantity of heat by volume. | Percentage of coke by weight. |
|---|---|---|---|---|---|
| Anthracite. | |||||
| Beaver Meadow, | Pa. | 88.9 | 10.4 | 94 | |
| Forest Improvement, | Pa. | 90.7 | 10.8 | 94 | |
| Lehigh, | Pa. | 89.1 | 9.6 | 94 | |
| Lackawanna, | Pa. | 87.7 | 10.7 | 94 | |
| Coke. | |||||
| Midlothian, | Va. | 10.3 | 92 | .66 | |
| Cumberland, | Md. | 10.3 | 92 | .75 | |
| Bituminous. | |||||
| Maryland, | Md. | 73.5 | 11.2 | 85 | |
| Cumberland, | Md. | 74.3 | 11.0 | 85 | |
| Blossburg, | Pa. | 73.4 | 10.9 | 85 | .83 |
| Karthans, | Pa. | 73.8 | 9.8 | 85 | .88 |
| Cambria County, | Pa. | 69.4 | 10.2 | 85 | |
| Clover Hill, | Va. | 56.8 | 8.5 | 85 | .68 |
| Tippecanoe, | Va. | 64.6 | 8.5 | 85 | |
| Pittsburgh, | Pa. | 55.0 | 8.9 | 85 | .68 |
| Missouri, | Mo. | .57 |