Lord Warrington of Clyffe, J.:-

The action in which the present appeal arises is one for the infringement of the Canadian Patent No. 208,583, the application for which was made on 17th September 1920. The application was made by the inventor, Ernest Alexanderson. The Patent was dated 15th February 1921, and was granted to the present appellants as assignees of Alexanderson.

That the patent was infringed by the respondents is admitted, but they dispute its validity on several grounds, including those hereinafter specifically mentioned.

The trial Judge Maclean in the Exchequer Court of Canada held that none of the grounds of defence was established, and on 14th April 1927, he pronounced a decree whereby it was declared and adjudged that the patent was valid and that it had bad been infringed by the respondents, and an injunction with ancillary relief, including an enquiry as to damages, was granted.

The respondents appealed to the Supreme Court of Canada, who on 7th February 1928, made an order allowing the appeal, reversing the judgment of the Exchequer Court, and dismissing the action with costs.

The present appeal is brought by special leave of His Majesty in Council granted by Order i