NOTE.—A shorter method of calculating by .7854 in larger sums is to
multiply by 11 and divide by 14, for decimal .7855 = the fraction
11/14th. Note: .7854 is the area of a circular inch.
When valves rise from their seats under increasing steam pressure
they do so by a constantly diminished ratio which has been carefully
determined by experiment and reduced to the following table.
+----------------+----------------+
|Pressure in Lbs.| Rise of Valve. |
+----------------+----------------+
| 12 | 1-36 |
| 20 | 1-48 |
| 35 | 1-54 |
| 45 | 1-65 |
| 50 | 1-86 |
| 60 | 1-86 |
| 70 | 1-132 |
| 80 | 1-168 |
| 90 | 1-168 |
+----------------+----------------+
The following useful table was prepared by the Novelty Iron Works, New
York.
+----------------+----------------+
|Boiler Pressure |Area of Orifice |
| in Lbs. Above | in Sq. In. for |
|the Atmosphere. |Each Sq. Ft. of |
| |Heating Surface.|
+----------------+----------------+
| 0.25 | .022794 |
| 0.5 | .021164 |
| 1. | .018515 |
| 2. | .014814 |
| 3. | .012345 |
| 4. | .010582 |
| 5. | .009259 |
| 10. | .005698 |
| 20. | .003221 |
| 30. | .002244 |
| 40. | .001723 |
| 50. | .001389 |
| 60. | .001176 |
| 70. | .001015 |
| 80. | .000892 |
| 90. | .000796 |
| 100. | .000719 |
| 150. | .000481 |
| 200. | .000364 |
+----------------+----------------+