On farms of moderate size it is usual to hire steam tackle as required, the outlay involved in the purchase of a set being justifiable only in the case of estates or of very big farms where, when not engaged in ploughing, or in cultivating, or in other work upon the land, the steam-engine may be employed in threshing, chaff-cutting, sawing and many similar operations which require power.
The thermal efficiency of a steam-engine is in general increased by carrying out the expansion of the steam in two, three or even more stages in separate cylinders, notwithstanding the inevitable drop of pressure which must occur when the steam is transferred from one cylinder to the other during the process of expansion.
Table Xxi It is instructive to inquire into the limiting efficiency of an engine consistent with the conditions under which it is working, because in no case can the efficiency of a steam-engine exceed a certain value which depends upon the temperatures at which it receives and rejects heat.
The most usual way of providing this power is by the combustion of coal in the fire-box of a boiler and the utilization of the steam produced in a steam-engine, both boiler and engine being carried on a frame mounted on wheels in such a way that the crank-shaft of the steam-engine becomes the driving-axle of the train.
He was a voluminous writer on subjects directly connected with his chair, and, besides contributing almost weekly to the technical journals, such as the Engineer, brought out a series of standard textbooks on Civil Engineering, The Steam-Engine and other Prime Movers, Machinery and Millwork, and Applied Mechanics, which have passed through many editions, and have contributed greatly to the advancement of the subjects with which they deal.
Besides its copper works the town at present possesses extensive tinplate, steel and galvanized sheet works as well as iron and brass foundries, steam-engine factories, brick and tile works, engineering works, flannel factories and chemical works.
The hearth may either rotate on an inclined axis, so that the path of its surface is oblique to that of the flame, or the working part may be a hollow cylinder, between the fireplace and flue, with its axis horizontal or nearly so, whose inner surface represents the working bed, mounted upon friction rollers, and receiving motion from a special steam-engine by means of a central belt of spur gearing.