Any summons or notice, or any writ or other proceeding at law or equity, required to be served upon the promoters of the undertaking may be served by the same being left at or transmitted through the post, directed to the principal office of the promoters of the undertaking, or one of the principal offices where there shall be more than one, or being given personally, or transmitted through the post, directed to the secretary, or in case there be no secretary then by being given to the solicitor of the said promoters.