(a) B contracts to build a ship for C for a given sum, to be paid by instalments as the work reaches certain stages. A becomes surety to C for B' s due performance of the contract. C, without the knowledge of A, prepays to B the last two instalments. A is discharged by this prepayment.

(b) C lends money to B on the security of a joint and several promissory note made in C' s favour by B, and by A as surety for B, together with a bill of sale of B' s furniture, which gives power to C to sell the furniture, and apply the proceeds in discharge of the note. Subsequently, C sells the furniture, but, owing to his misconduct and wilful negligence, only a small price is realized. A is discharged from liability on the note.

(c) A puts M as apprentice to B, and gives a guarantee to B for M' s fidelity. B promises on his part that he will, at least once a month, see M make up the cash. B omits to see this done as promised, and M embezzles. A is not liable to B on his guarantee.