A tool is usually more simple than a machine; it is generally used with the hand, whilst a machine is frequently moved by animal or steam power.

The difference between a tool and a machine is not capable of very precise distinction; nor is it necessary, in a popular explanation of those terms, to limit very strictly their acceptation.

At each increase of knowledge, as well as on the contrivance of every new tool, human labour becomes abridged.

Another mode of accumulating power arises from lifting a weight and then allowing it to fall.

Errors using inadequate data are much less than those using no data at all.

Some kinds of nails, such as those used for defending the soles of coarse shoes, called hobnails, require a particular form of the head, which is made by the stroke of a die.