(d) where a substitute is engaged in the place of a seaman who duly signed the agreement and whose services are, within 24 hours of the ship proceeding to sea, lost by death, desertion or other unforeseen cause, the master shall, before the ship proceeds to sea if practicable, and if not, as soon as possible afterwards, cause the agreement to be read over and explained to the substitute, and the substitute shall thereupon sign the same in the presence of a witness and the witness shall attest the signature;