(4)Where a person, having contracted for the purchase of any property but not having obtained a conveyance thereof, contracts to sell the whole, or any part thereof to any other person or persons, and the property is in consequence conveyed by the original seller to different persons in parts in conveyance of each part sold to a sub-purchaser shall be chargeable with ad valorem duty in respect only of the consideration paid by such sub-purchaser, without regard to the amount or value of one original consideration; and the conveyance of the residue (if any) of such property to the original purchaser shall be chargeable with ad valorem duty in respect only of the excess of the original consideration over the aggregate of the considerations paid by the sub- purchasers :Provided that the duty on such last-mentioned conveyance shall in no case be less than one rupee.
