§9. The clause containing the power last quoted, gives power also to "fix the standard of weights and measures." For the convenience of trade between the states, the standard of weights and measures should be the same in all the states. Without such uniformity, commerce among the states would meet with embarrassments scarcely less than those experienced from the want of a uniform currency. To effect the desired object, this power was given to congress. §10. The next power in the list is the power "to provide for the punishment of counterfeiting the securities and current coin of the United States." By securities here are meant bonds and other evidences of debt. As the general government has the power to borrow money and to coin money, it is proper that it should also have the power to provide for punishing those who forge its written obligations for the payment of the money borrowed, and who counterfeit its coin. These offenses are tried in the courts of the United States. Chapter XXXV. Powers of Congress in relation to Post-Offices, Copy-Rights, and Patents, and Inferior Courts. §1. Congress has power "to establish post-offices and post-roads." The post-office department, from the facilities which it affords for the circulation of intelligence and the transaction of business, is an institution of incalculable value to the union. It is impossible to conceive all the difficulties which would attend the exercise of this power by the different states. A uniform system of regulations is indispensable to the efficiency of this department, and could be secured only by placing this power in the hands of congress. §2. Congress has power "to promote the progress of science and the useful arts, by securing, for limited times, to authors and inventors, the exclusive right to their respective writings and discoveries." Useful sciences and arts are promoted by new books and new inventions. But if every man had the right to print and sell every book or writing, without compensation to the author, there would be little to encourage men of ability to spend, as is often done, years of labor in preparing new and useful works. Nor would men of genius be likely to spend their time and money in inventing and constructing expensive machinery, if others had an equal right to make and sell the same. In pursuance of the power here given, congress has enacted laws for the benefit of authors and inventors. §3. The exclusive right of an author to the benefits of the sale of his books or writings, is called _copy-right_, and is obtained thus: The author sends a printed copy of the title of his book to the clerk of the district court of the United States of the district in which the author resides. The clerk records the title in a book, for which he receives fifty cents, and gives the author, under the seal of the court, a copy of the record, for which also he receives fifty cents.