Whenever anything really practical has been invented, it has been done by a person without practical knowledge of that particular subject. Take, for instance, the modern postage stamp. It would be most natural to assume that it was invented by some practical post office official. It was not. At the beginning of the last century it was a complicated affair to mail a letter. In order to dispatch a letter one had to go to the nearest receiving office where various books had to be referred to and many other formalities complied with. The uniform rate of postage known today is hardly sixty years old, and our present postage stamp that makes this possible was not invented by a practical postal employee at all but by someone completely outside the post office.