Author of "A Treatise on Copyright in Design," " Counsel to Inventors," &c. &c. LONDON: JOHN CROCKFORD, 29, ESSEX STREET, STRAND. 1851. PREFACE. AN attempt is here made to advance the theory of a subject of jurisprudence which presents some very peculiar and some rather subtle features. "The whole of the Patent Law," says the present Master of the Rolls (Evidence, House of Lords Committee, 1851), "is exceedingly difficult, particularly in practice. Nobody I have ever yet known has been able to arrive at a satisfactory definition, precisely to ascertain in any case what is a new and what is a useful invention. The cases at law (which are very numerous) give a sort of rough definition of the matter, but the judges have found themselves totally at a loss to do more than decide in each individual case." Of these cases a selection is here given (with some preference to recent decisions, and including some which are not in the standard reporters), and used, not so much for authoritative precept, which, indeed, they often do not furnish, as for illustration of the principles. These, though few and simple, occur in combinations infinitely varied by the special facts, and it seemed expedient to |