3_C²l_ ------ = _d_ 64,4557.1 cu. ins. 4π 5. Revolutions during 24 hours, _N_ 43,337 6. Weight of one cubic foot of water, _w_ 62.42 lbs. 7. Total head pumped against, _H_ 266.61 ft. 8. Total feed-water per 24 hours, _W_ 160,354 lbs. 9. Duty per 1000 lbs. of feed-water = _d × w H × N_ × 1000 ------ × ------------- 1728 _W_ 266.61 × 43,337 × 1000 = 2,331,976 × ---------------------- = 168,027,200 ft.-lbs. 160,354 10. Percentage of moisture in steam at engine-throttle valve 0.3 per cent. 168,027,200 11. Duty per 1000 lbs. of dry steam, ----------- = 168,532,800 0.997 ft.-lbs. DUTY PER MILLION HEAT-UNITS. 12. Average steam pressure at throttle above atmosphere. 173 lbs. 13. Average feed-water temperature. 78°.5 Fahr. 14. Total heat in one pound of steam containing 0.3 per cent. of moisture above 32° Fahr. 1,194.2 B. T. U. 15. Heat per lb. of feed-water above 32° Fahr. 46.5 ” ------- 16. Heat supplied per lb. of feed-water above 32° Fahr. 1,147.7 ” 17. Duty per lb. of feed-water. 168,027.2 ft.-lbs. 18. Duty per million B. T. U. 146,403,614 ” =203. Conditions Affecting Duty of Pumping-engines.=—Manifestly the duty of a pumping-engine by whatever standard it may be measured will vary with the conditions under which it is made. A new engine running under the favoring circumstances of a short-time test may be expected to give a higher duty than when running under the ordinary conditions of usage one month after another. Hence it can scarcely be expected that the monthly performance, and much less the yearly performance, of an engine will show as high results as when tested for a day or two or for less time. =204. Speeds and Duties of Modern Pumping-engines.=—The following table gives the piston or plunger speeds of a number of the best modern pumping-engines, and the corresponding duties, with the standards by which those duties are measured.