Mr. Johnston's book (Google Books ⧉, Amazon ⧉, Bookshop ⧉)

The Boy Travellers on the Congo: Adventures of Two Youths in a Journey with Henry M. Stanley Through the Dark Continent

Perhaps Doctor Bronson will tell us something about it, as he has been reading Mr. Johnston's book, describing the exploration to it. A very interesting book it is, though less so to the general reader than to the scientific one. Mr. Johnston is, as you know, a naturalist, and the principal part of the book is devoted to his special line of study.