Two books this time which may be the result of the success of Slim, and certainly directed to the same market. (See Dark Canyon, page 20). This is a good picture of the dangers, mechanics and personnel of tunnel building -- a dramatization of one phase of our mechanical civilization which we take more or less on faith. Scorcher and Jumbo, the two ""leads"", are to be played in a film version of the story by Victor McLaglen and Edmund Lowe, and the picture may give an impetus to the book. As it stands, the market is primarily men who are interested in factual fiction, and old boys.