When what is to be delivered is a determinate thing, the creditor, in addition to the right granted him by Article 1170, may compel the debtor to make the delivery. If the thing is indeterminate or generic, he may ask that the obligation be complied with at the expense of the debtor. If the obligor delays, or has promised to deliver the same thing to two or more persons who do not have the same interest, he shall be responsible for any fortuitous event until he has effected the delivery