A great part of the machines made use of in those manufactures in which labour is mostsubdivided, were originally the inventions of common workmen, who, being each of thememployed in some very simple operation, naturally turned their thoughts towards finding outeasier and readier methods of performing it. Whoever has been much accustomed to visit suchmanufactures must frequently have been shown very pretty machines, which were theinventions of such workmen in order to Nike Free Run 2 Sale facilitate and quicken their particular part of the work.In the first fire-engines, a boy was constantly employed to open and shut alternately thecommunication between the boiler and the cylinder, according as the piston either ascended ordescended. One of those boys, who loved to play with his companions, observed that, by tyinga string from the handle of the valve which opened this communication to another part of themachine, the valve would open and shut without his assistance, and leave him at liberty todivert himself with his playfellows. One of the greatest improvements that has been madeupon this machine, since it was first invented, was in this manner the discovery of a boy whowanted to save his own labour.All the improvements in machinery, however, have by no means been the inventions ofthose who had occasion to use the machines. Many improvements have been made by theingenuity of the makers of the machines, when to make them became the business of apeculiar trade; and some by that of those who are called philosophers or men of speculation,whose trade it is not to do anything, but to observe everything; and who, upon tha t account,are often capable of combining together the powers of the most distant and dissimilar objects.In the progress of society, philosophy or speculation becomes, like every other employment,the principal or sole trade and occupation of a particular class of citizens. Like every otheremployment too, it is subdivided into a Nike Air Max 1 Mens great number of different branches, each of whichaffords occupation to a peculiar tribe or class of philosophers; and this subdivision ofemployment in philosophy, as well as in every other business, improves dexterity, and savestime. Each individual becomes more expert in his own peculiar branch, more work is doneupon the whole, and the quantity of science is considerably increased by it.