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 in Council dated 30th July 1928.

Among the grounds of defence raised by the respondents it is necessary to mention the following only, viz., (1) lack of subject matter having regard to the state of the art as shown by earlier patent specifications; (2) lack of utility; (3) anticipation by a specification of a German patent granted on 23ed June 1919 to Schloemilch and Von Bronk on an application made on 9-02-1913. The specification, however, remained unpublished until the grant of the patent; (4) A defence founded on S. 7, Patent Act of 1906, which provides that the invention claimed shall be one which amongst other things, "was not known or used by any other person before the claimant's invention thereof."

A further defence was raised founded on the fact that Alexanderson's declaration in support of his application stated contrary to the fact that he had not applied for or obtained a patent for the invention in a foreign country.

It will be convenient to deal with these defences in order, except that No. 2 (want of utility) may be disposed of at once, inasmuch as it was not seriously pressed before the Board.

The patent relates to wireless telegraphy, or rather, to wireless telephony, and in particular to the selection in a receiving apparatus of oscillations of a given wave-length from mixed oscillations. This quality of a receiving apparatus is conveniently referred to as "selectivity.” Speaking generally, the object of the inventor was to increase the selectivity of the apparatus and at the same time to avoid loss of strength in the selected oscillations.

The chief elements in a radio receiving apparatus,' their functions and operation, are so fully described by Maclean, J. in his judgment (Record, pp. 390-391), that it is unnecessary to repeat them. It is sufficient to say that at a receiving station it is necessary to eliminate from the infinite number of waves reaching the antennae or aerial all except those of the desired wave-length, and that this is achieved by the use of a tuned circuit containing a condenser. The condenser contains two sets of plates, one of which may he made moveable or variable with respect to the other, thus varying the capacity of the condenser and adjusting the resonant frequency so as to correspond to the frequency of the desired wave. A variable condenser is conventionally distinguished in drawings of an apparatus by an arrow drawn through the lines representing the condenser. Another conventional sign is an arrowhead pointing to the secondary of the induction coil. This indicates that the number of turns of the coil may be changed, thus varying the inductance or the voltage of the induction circuit, and as a consequence the resonant frequency thereof.

It will be convenient, in the first instance, to deal with the two ques