Secondly, there is #a great deal of time lost when a man changes from one kind of work to another# many times in the day. Before you can make a thing you must get all the right tools and materials around you; when you have finished one box, for instance, you are all ready to make another with less trouble than the first; but if you have to go off and do something quite different, such as to mend a pair of shoes or write a letter, a different set of implements have to be got ready. A man, as Adam Smith thought, saunters a little in turning his hand from one kind of employment to another, and if this happens frequently, he is likely to become lazy. In the third place, Smith asserted that #the division of labour leads to the invention of machines# which abridge labour, because men, he thought, were much more likely to discover easy methods of attaining an object when their whole attention is directed to that object. But it seems doubtful how far this is correct. Workmen do occasionally invent some mode of lessening their labour, and a few important inventions have been made in this way. But, as a general rule, the division of labour leads to invention, because it enables ingenious men to make invention their profession. The greatest inventors, such as James Watt, Bramah, Fulton, Roberts, Nasmyth, Howe, Fairbairn, Whitworth, the Stephensons, Wheatstone, Bessemer, Siemens, have not been led to invention in the way described by Adam Smith, but have cultivated an original genius by careful study and long practice in mechanical construction. But the division of labour greatly assists invention, because it enables each factory to adopt particular kinds of machinery. In England the division of labour is continually becoming more and more minute, and it is not uncommon to find that the whole supply of some commodity is furnished from a single manufactory, which can then afford to have a set of machines invented on purpose to produce this one commodity. Such is even more the case in the large manufactories of the United States. I will now describe four other ways in which great saving of labour arises from the division of labour, as follows:--