The district may be extended so as to include territory not previously included within its boundaries in the same manner as hereinbefore prescribed for the original establishment of a district. The cost of the extension shall include all the costs and expenses occasioned by reason of such extension and in addition thereto such proportion of the cost of the system of the original district as the county government shall determine.

9 Del. C. 1953, § ?4618; 56 Del. Laws, c. 103, § ?13;