38 CAP. 400] Patents the time of the endorsement, precluded by a contract in which the claimant is interested from granting licences under the patent may apply to the Registrar for cancellation of the endorsement. (3) Where the Registrar is satisfied, on application made under subsection (2), that the patentee is and was precluded as aforesaid, he shall' cancel the endorsement, and thereupon the patentee shall be liable to pay, within such period as may be prescribed, a sum equal to the balance of all renewal fees which would have been payable if the patent had not been endorsed, and if that sum is not paid within that period the patent shall cease to have effect at the expiration of that period. (4) Where the endorsement of a patent is cancelled under this sec­ tion, the rights and liabilities of the patentee with respect to it shall thereafter be the same as if the endorsement had not been made. (5) An applicant shall advertise in the prescribed manner any application made by. him under this section and within the prescribed period after such advertisement­ (a) in the case of an application under subsection (1), any per­ son interested; and (b) in the case of an application under subsection (2), the patentee and either additionally or alternatively any person interested; . . may give notice to the Registrar of opposition to the cancellation. (6) Where any such notice of opposition is given, the Registrar shall fix a date for the hearing of the application and shall advise in writing the parties of the date so fixed, and shall, after giving the applicant and the opponent an opportunity to be heard, give such decision on the application as he may consider just. (7) An application made under this section for the cancellation of the endorsement of a patent of addition shall be treated as an appli­ cation for the cancellation of the endorsement of the patent for the main invention also, and an application made under this section for the cancellation of the endorsement of a patent in respect of which a patent of addition is in force shall be treated as an application for the cancellation of the endorsement of the patent of addition also. (8) An appeal shall lie from any decision of the Registrar under this section. Compulsory licencein case of abuse or insufficient use of patent rights 37. (1) Subject to the provisions of subsection (14), any person interested who can show that he has been unable to obtain a licence under a patent on reasonable terms may, after the expiration of a period of three years subsequent to the date on which that patent was sealed or four years subsequent to the date on which the appli­ cation in respect thereof was lodged, whichever period last expires,