They started work on the following morning.  From the rocky banks of the stream they rolled down a number of stones and boulders and piled them in the channel to the height of the ridge, forming two adjacent sides of a square.  Then up stream they cut a quantity of brushwood, which, being set afloat, was carried by the water against the piled-up stones.  This occupied them the whole day, and they left for the next the final operation—the digging of earth to stop up the interstices through which the water still flowed away, and the carrying of it in wheelbarrows to its dumping places.