Inventions in their nature being for the good of all men and for all time, it has been deemed wise by all nations in their legislation not to permit the inventor to lock up his property in secret, or confine it to his own use; and hence the universal practice is to enact laws giving him, his heirs, and assigns, exclusive ownership to this species of his property for a limited time only, adjudged sufficient to reward him for his efforts in its production, and to encourage others in like productions; while he, in consideration for this protection, is to fully make known his invention, so that the public may be enabled to freely make and use it after its exclusive ownership shall have expired. In addition to the motives and incentives mentioned inducing this modern mighty outflow of inventions, regard must be had to the conditions of personal, political and intellectual freedom, and of education. There is no class of inventors where the mass of men are slaves; and when dense ignorance abounds, invention sleeps. In the days of the greatest intellectual freedom of Greece, Archimedes, Euclid, and Hero, its great inventors, flourished; but when its political _status_ had reduced the mass of citizens to slaves, when the work of the artisan and the inventor was not appreciated beyond the gift of an occasional crown of laurel, when manual labour and the labourer were scorned, inventions were not born, or, if born, found no nourishment to prolong their lives. In Rome, the labourer found little respect beyond the beasts of burden whose burdens he shared, and the inventor found no provision of fostering care or protection in her mighty jurisprudence. The middle ages carefully repressed the minds of men, and hid away in dark recesses the instruments of learning. When men at length awoke to claim their birthright of freedom, they invented the printing-press and rediscovered gunpowder, with which to destroy the tyranny of both priests and kings. Then arose the modern inventor, and with him came the freedom and the arts of civilisation which we now enjoy. What the exercise of free and protected invention has brought to this century is thus summarised by Macaulay: