Large 4to. With double-page route map printed in color & 12 full-page mounted chromolithograph plates. Original publisher's gilt pictorial green cloth (rebacked and recornered in morocco, endpapers renewed).FIRST EDITION. "The voyage of H.M.S. 'Challenger', between the years 1872 and 1876, must always occupy a distinguished place in the annals of geographical discovery, as being the first systematic attempt made on a large scale to explore the depths of the ocean - hitherto generally deemed unfathomable" (Preface). Du Rietz 1347; Ferguson 18556; Spence 1258.