Each, however, continues to perform its own duty, and nothing else. No effect is produced, no result follows, from the joint use of the two.

A handle in common, a joint handle, does not create a new or combined operation. The handle for the pencil does not create or aid the handle for the eraser. The handle for the eraser does not create or aid the handle for the pencil. Each has and each requires a handle the same as it had and required, without preference to what is at the other end of the instrument; and the operation of the handle of and for each is precisely the same, whether the new article is or is not at the other end of it. In this and the cases supposed you have but a rake, a hoe, a hammer, a pencil, or an eraser, when you are done. The law requires more than a change of form, or juxtaposition of parts, or of the external arrangement of things, or of the order in which they are used, to give patentability. Curtis on Pat., sect. 50; Hailes v. Van Wormer, 20 Wall. 353. A double use is not patentable, nor does its cheapness make it so. Curtis, secs. 56, 73. An instrument or manufacture which is the result of mechanical skill merely is not patentable. Mechanical skill is one thing: invention is a different thing. Perfection of workmanship, however much it may increase the convenience, extend the use, or diminish expense, is not patentable. The distinction between mechanical skill, with its convenience and advantages and inventive genius, is recognized in all the cases. Rubber Tip Pencil Co. v. Howard, and other cases, supra; Curtis sect. 72b.

The combination, to be patentable, must produce a different force or effect, or result in the combined forces or processes, from that given by their separate parts. There must be a new result produced by their union: if not so, it is only an aggregation of separate elements.