Nevertheless, the fundamental principles of construction embodied in this first typewriter still survive, though their application has since been modified or transformed in the march of improvement. In this original machine we find the escapement or step-by-step "pulse beat," which causes the letter spacing, we find the type bars hung in such a manner that the type all strike the paper at a common printing point, and we find a mechanism for the return of the carriage and line spacing of the cylinder. Most interesting of all, we find the "universal keyboard" in very nearly its present form. This was not an innovation introduced by Jenne or any of his co-workers, for, tracing back to the Sholes and Glidden model of the previous year, we find a very close approach to the same thing. Who invented the universal keyboard?--meaning the present universal arrangement of the letters on the typewriter keys. Of all the questions concerning the origin of the typewriter or any of its features, this is the one most frequently asked. The answer is that the universal keyboard, with some minor variations, has been standard since the invention of the writing machine. Some believe that the universal keyboard was invented by Alexander Davidson, a mechanic and surveyor of West Virginia, who was also one of the pioneers in the field of commercial education. It is known that Davidson, in the later seventies, made a special study of the subject of scientific keyboard arrangement. But there is no evidence that Davidson ever saw a typewriter before the year 1875, at which time the keyboard had already assumed the "universal" form. It is positively known that Densmore and Sholes, laboring together, worked out the universal arrangement of the letter keys. Just how they happened to arrive at this arrangement, however, is a point on which there has always been much speculation. It must be remembered that both of these men were printers by trade, a most important point in this connection. The usual a b c arrangement of letters, which would naturally suggest itself to the ordinary layman, means nothing to a printer, who is more familiar with the arrangement of the type in the printer's case. Here, however, we encounter the fact that the arrangement of the letters on the universal keyboard is nothing like the arrangement of the type in the printer's case. The truth seems to be that the arrangement of the universal keyboard was mainly influenced by the mechanical difficulties under which Sholes labored. The tendency of the type bars on all the Sholes models was to collide and "stick fast" at the printing point, and it would have been natural for Sholes to resort to any arrangement of the letters which would tend to diminish this trouble. These mechanical difficulties are now of the past, but time has proved and tested the universal keyboard, and has fully demonstrated its efficiency for all practical needs.