Hypothecation is a contract of pledge, … usually effectd by a deed called a bottomry bond, by which the master bind himself in a penalty to repay the sum borrowed… When the cargo alone hypothecated, the instrument used to be called a respondentia bond;
A Compendium of the Law of Merchant Shipping, 3rd Edition, 1864, F. Maude, C. E. Pollock, pp.433-434
Per Sir W.Scott in The Gratitudine  EngR 525; (1801) 3 C Rob 240 at p.264:
… it is now well known that usury within the statue is taking a higher interest for the loan of money to be repaid in all events than the statue allow. On principle, therefore, the right of hypothecation of the whole cargo is extremely natural, and if I am right in considering it as equivalent to a sale of a part, it is little more that what all the books of maritime jurisprudence direct to be done; it is in truth but a power to make a partial sale, conducted with greater probability of ultimate advantage to the whole; for as all must finally contribute in the case of an actual sale of a part, what new hardship is imposed? All contribute in this, as a portion of the whole value of the cargo is abraded for the general benefit, probably with less inconvenience to the parties, than if any of person’s whole adventure of goods had been sacrificed by a disadvantageous sale in the first instance.
Per Sir Christopher Robinson in The Cognac  EngR 463; (1832) 2 Hag Adm 377 at p.387:
Writers on maritime law treat generally of the contracts of respondentia and bottomry under the same head with very little discrimination, as the are similasr in their principal character of maritime risk and interst, and are so considered together in countries where contracts of repondentia still exist. In this country, that description of bottomry has been disused since the passing of 19 GII, c 37; and therefore, we are not so much in the habbit of illustrating the one by the other. But it is considered that respondentia bonds are entered into on far more advantageous terms between the contracting parties who know each other, and may be able to judgge for themselves of the state of the money market, and of the risk and profits on which money so employed migth be advanced, - whilst in bottomry by the master, like the present, the owner is usually ignorant of all that passes, and the master has no other authority to pledge his property than what is derived from the necessity in which he is placed…