mortgage-money, and agrees, expressly or impliedly, that, in the event of his failing to pay according to his contract, the mortgagee shall have a right to cause the mortgaged property to be sold and the proceeds of sale to be applied, so far as may be necessary, in payment of the mortgage-money, the transaction is called a simple mortgage and the mortgagee a simple mortgagee. (c) Mortgage by conditional sale.—Where the mortgagor ostensibly sells the mortgaged property— on condition that on default of payment of the mortgage-money on a certain date the sale shall become absolute, or on condition that on such payment being made the sale shall become void, or on condition that on such payment being made the buyer shall transfer the property to the seller, the transaction is called a mortgage by conditional sale and the mortgagee a mortgagee by conditional sale: Provided that no such transaction shall be deemed to be a mortgage, unless the condition is embodied in the document which