Thus we travelled on day after day; but we made but slow progress through the densely-wooded country, having sometimes to cut our way amid the trees, though we were generally able to find a passage without felling them.  Occasionally, however, we were compelled to do even that, and to drag the huge trunks out of the road, before the waggons could proceed.  We had also frequently to cross rivers.  When no ford could be found, we built large rafts, on which the waggons were ferried over, while the oxen gained the opposite bank by swimming.  They were accustomed to the undertaking; and, strange as it may seem, we never lost any by this means.