(279.) If each of the ropes, instead of being attached to fixed points at the top, are carried over fixed pulleys, and attached to the several moveable pulleys respectively, as in _fig. 127._, the power of the machine will be greatly increased; for in that case the forces which stretch the successive ropes increase in a treble instead of a double proportion, as will be evident by attending to the numbers which express the tensions in the figure. One rope would render the weight three times the power, two ropes nine times, three ropes twenty-seven times, and so on. An arrangement of pulleys is represented in _fig. 128._, by which each rope, instead of being finally attached to a fixed point, as in _fig. 126._, is attached to the weight. The weight is in this case supported by three ropes; one stretched with a force equal to the power; another with a force equal to twice the power; and a third with a force equal to four times the power. The weight is therefore, in this case, seven times the power. (280.) If the ropes, instead of being attached to the weight, pass through wheels, as in _fig. 129._, and are finally attached to the pulleys above, the power of the machine will be considerably increased. In the system here represented the weight is twenty-six times the power. (281.) In considering these several combinations of pulleys, we have omitted to estimate the effects produced by the weights of the sheaves and blocks. Without entering into the details of this computation, it may be observed generally, that in the systems represented in _figs. 126._, _127._ the weight of the wheel and blocks acts against the power; but that in _figs. 128._ and _129._ they assist the powers in supporting the weight. In the systems represented in _fig. 123._ the weight of the pulleys, to a certain extent, neutralise each other.