TWO:The EndOther reasons for the extended and general use of steam as a power, besides those already named, are to be found in the fact that no other available element or substance can be expanded to a given degree at so small a cost as water; and that its temperature will not rise to a point injurious to machinery, and, further, in the very important property of lubrication which steam possesses, protecting the frictional surfaces of pistons and valves, which it is impossible to keep oiled because of their inaccessibility or temperature.








