Across the great craterland to the Congo : a sequel to "The wonderland of the eastern Congo" : describing a journey of exploration and research to the land of the giant craters in Tanganyika territory, and to the forests, lakes, and volcanoes of the south-eastern Congo : with some account of the african apes, and the capture and training of the african elephant / by T. Alexander Barns,... ; with an introduction by J. W. Gregory