12. On the day fixed under section 9 or on any other day to which the inquiry has been adjourned, the Collector shall proceed to inquire into the objections (if any) which any person interested has stated pursuant to a notice given under the said section to the measurements made under section 8, and into the decrease in the value of the land, and into the respective interests of the persons claiming the compensation, and shall make an award under his hand of- (a) the true area of the land and the nature of the obstructions from which the land is to be kept free; (b) the compensation which in his opinion should be allowed for any damage caused or to be caused under section 6 and for any restrictions imposed under section 7; and (c) the apportionment of the said compensation among all the persons known or believed to be interested in the land, of whom or of whose claims he has information, whether they have respectively appeared before him or not.