...been originally granted for the term of twenty-one years. And the benefit of such renewal shall extend to assignees and grantees of the right to use the thing patented, to the extent of their respective interest therein: Provided, however, That no extension of a patent shall be granted after the expiration...

...and not for a machine or machinery; and that the act of Congress, extending the benefit of renewals to assignees and grantees of the right to use the thing patented, when properly construed, does not include patents for a process, but should be confined to patents...