The saving in power, by using a sharp saw, is very great. It has never yet been measured in power-saws, and is hardly measurable in hand-saws; but it is without doubt consider able. By using sharp saws, thinner blades may be used than where the teeth are dull; because the duller the saw the more power required to drive it through the wood, and the more strain on each tooth separately, and on the blade as a whole. For the same reason, longer teeth may be used where they are sharp, than where they are dull.