How did Gulliver relieve himself?

From the text:

Soon after I heard a general shout, with frequent repetitions of the words Peplom selan; and I felt great numbers of people on my left side relaxing the cords to such a degree, that I was able to turn upon my right, and to ease myself with making water; which I very plentifully did, to the great astonishment of the people; who, conjecturing by my motion what I was going to do, immediately opened to the right and left on that side, to avoid the torrent, which fell with such noise and violence from me.