Section 12. If a proprietor fails to pay an assessment for six months after demand therefor by the collector or other proper officer, or after a notice of such assessment posted and published in the manner prescribed for the first meeting, the committee of the proprietors or other officers authorized by them for that purpose may sell by public auction and give to the purchaser a deed of so much of the right or share of such proprietor as is sufficient to pay the amount so due from him and all the reasonable charges of the sale, first giving thirty days’ notice of the time and place appointed for such sale in the manner prescribed for notifying the first meeting.