The smoother we make the pulley the more nearly does the amount of useful work which the weight is capable of doing approach ro foot-pounds, and if we take into account the work done against the friction of the pulley, we may say that the work done by the descending weight is ro foot-pounds, and hence when the weight is in its elevated position we have at disposal r o foot-pounds more energy than when it is in the lower position.
The gradient or grade of a line is the rate at which it rises or falls, above or below the horizontal, and is expressed by stating either the horizontal distance in which the change of level amounts to r ft., or the amount of change that would occur in some selected distance, such as roo ft., r000 ft.
In America a gradient of r in roo is often known as a r% grade, one of 2 in roo as a 2% grade, and so on; thus a 0-25% grade corresponds to what in England would be known as a gradient of r in 400.
An incline of r in 400 is reckoned easy, of r in 200 moderate and of r in roo heavy.
But the flank attack became entangled in mass in a loop of the river and suffered heavily, and two batteries that formed part of the frontal attack came into action within a few hundred yards of unsuspected Boer trenches, with the result that ten guns were lost, as well as in all some r roo men.
