35° THE POPULAR SCIENCE MONTHLY 



was DO haste in publication ; aside from some very brief communications 

 to societies, nothing appeared until 1839, when the Journal of Re- 

 searches was printed. Owen's descriptions of the fossil mammalia was 

 issued in 1840 with an introduction by Darwin and the final publica- 

 tion of results was made in three parts, dated 1842, 1844 and 1846. 

 Thus early in his career, Darwin showed that caution which character- 

 ized him throughout life, an indifference to priority which was the out- 

 growth of his love of accuracy. 



Part 2 of the " Geological Observations," dated 1844, relates chiefly 

 to volcanic islands. In most cases the stay at those was brief and the 

 studies were fragmentary; yet Darwin saw enough to let him discuss 

 the origin of volcanic cones, to determine some cardinal points respect- 

 ing the distribution of the islands, to distinguish submarine from sub- 

 aerial lava flows and to prove that experimental studies on metamor- 

 phosis of limestones had led to very nearly true conceptions of the 

 process. 



As the coast survey of southern South America was the important 

 object of Captain Fitzroy's expedition, there was ample time for a good 

 reconnaissance of that region and Darwin spent nearly six months in 

 studying the pampas from the Parana and Uraguay rivers southward 

 almost to Magellan's Strait. A synopsis was given as an introduction 

 to Owen's Memoir, but the details did not appear until 1846, when they 

 were published as Part 3 of the " Geological Observations." The whole 

 subject was discussed attractively in the second edition of the Journal 

 of Researches. 



The superficial deposit of the great plains is a " reddish argillaceous 

 earth " containing concretions of indurated marl, which, at times become 

 continuous layers or even replace much of the red earth. In the north- 

 erly part of the plains-area, this pampas deposit, which passes down- 

 ward into sands, limestones and clays of late Tertiary age, yielded no 

 marine shells to Darwin; its infusoria, studied by Ehrenberg, proved 

 to be partly marine, partly freshwater, while the marly concretions re- 

 semble some freshwater limestones seen in Europe; but this paucity of 

 invertebrate life was unimportant, for the whole of that region proved 

 to be one vast cemetery, in which the skeletons of gigantic extinct 

 mammals are so numerous that a line could not be drawn in any 

 direction without passing through some bones. In northern Pata- 

 gonia the red deposit is bound closely to an overlying gravel, contain- 

 ing marine forms belonging to species now existing on the coast, 

 while in southern Patagonia marine shells occur in the pampas de- 

 posit itself. 



Darwin believed that this pampas material was deposited within 

 a vast estuary, into which great rivers carried from the surrounding 

 region carcasses of the animals whose skeletons were entombed in 



