Section 86.
The city council of the said town shall at the same time the tax for general purposes is levied, and at least once in each year, levy and collect a special tax on all taxable property in said town sufficient to raise money enough, which taken together with the net revenue derived during that year from any water works or light plant which may be erected or acquired with money derived from the sale of said bonds, will pay the semi-annual or annual interest on said bonds, and to pay one-twentieth of the face or par value of said bonds, which tax, when collected, shall be a sinking fund, and shall be used to pay semi-annual or annual interest and to pay said bonds on their maturity. Said tax to provide for said sinking fund may be included in other taxes of said town and considered a part thereof for the purpose of levying and collecting the same; but as fast as the tax is collected, its proportion to the other taxes collected with, or included in the sum collected shall be set apart from the other taxes as the aforesaid sinking fund, and shall only be used for the purpose of the semi-annual or annual interest on said bonds, and for the payment of said bonds on maturity and for no other purpose whatsoever.