The board of directors, at the time and place mentioned in said notice, or at such time or times to which the hearing of such petition may adjourn, shall proceed to hear the petition, and all objections thereto, presented in writing by any person, showing cause as aforesaid, why said petition should not be granted. The failure of any person interested to show cause, in writing, as aforesaid, shall be deemed and taken as an assent on his part to the inclusion of such lands in said district as prayed for in said petition.