constitutes the bargain regarding security requires registration under Section 17 of the Registration Act, 1908, as a non-testamentary instrument creating an interest in immovable property, where the value of such property is one hundred rupees and upwards. If a document of this character is not registered it cannot be used in the evidence at all and the transaction itself cannot be proved by oral evidence either.” xxx 14.2. But the question is whether a mortgage by deposit of title deeds is required to be done by an instrument at all. In our opinion, it may be effected in a specified town by the debtor delivering to his creditor documents of title to immovable property with the intent to create a security thereon. No instrument is required to be drawn for this purpose. However, the parties may choose to have a memorandum prepared only showing deposit of the title deeds. In such a case also registration is not required. But in a case in which the memorandum recorded in writing creates