Except as provided in §23-2, any person engaged in the business of distributing, manufacturing or furnishing gas, either natural, manufactured or mixed gas, in the City, shall be required to pay to the City an occupation tax in an amount equal to three cents per therm of all such gas distributed or furnished to the inhabitants of the City. Provided, however, the occupation tax shall be one cent per therm of all such gas transported within the city to transport customers.