the directors,in addition to the powers and authorities expressly conferred upon them by these Articles , may exercise all such powers and do all such acts as may be exercised or done by the company in general meeting subject nevertheless to the provisions of the companies ordinance, (chapter 622) , to these articles , and to any regulation from time to time made by the company in general meeting, provide that no regulation so made shall invalidate any prior act of the directors which would have been valid if such regulation had not been made