In fact, it was just such a boat as was needed on the trip the boys had in mind.  It had done excellent service on the Columbia, and nothing less could be expected of it on the Amazon.  The Wolf, which was merely a tender, was watertight in construction, being shaped like a banana, and was towed by the motor-boat.  Here the extra stocks of gasoline, provisions, and ammunition were packed.  The interior of the Wolf was about six feet by eighteen in size, while the distance from rounded floor to convex roof was about four feet.