Application of sinking fund

The aforesaid trustees may apply a sinking fund or any part thereof, in or towards the discharge of the loan or part of a loan for which such fund was created, and until such loan or part is wholly discharged shall not apply the same for any other purpose: Provided that when any loan or parts thereof have been consolidated under section 163, the trustees shall transfer to the sinking fund of the consolidated loan so created such part of the sinking funds of the original loans as may be proportionate to the amount of the original loans incorporated in the consolidated loan.