Page:The Journal of geology (IA journalofgeology11893univers).pdf/334

Amazon valley he examined the table-topped hills^[1] which Agassiz had referred to glacial action, and the boulders he had called "the only genuine erratic boulders" he had seen in the Amazon valley. Already, in 1867, Professor James Orton, who scouts the idea of the glaciation of the Amazonas, had discovered at Pebas, in the supposed glacial sediments, "marine or perhaps rather brackish water Tertiary fossils."^[2]

In 1871 Hartt found the supposed erratics of the Amazon valley to be boulders of decomposition derived from trap dikes near at hand, and stated that he "did not see, either at Ereré or in any part of the Amazonas, anything that would suggest glaciation."^[3] He still clung, however, to the idea that the highland of Brazil to the south had been glaciated.^[4]

Unfortunately Hartt has left no further record of his later views upon this subject, but that his views underwent a radical change I know as positively as one can know the opinions of another person. I went with him to Brazil in 1874, was with him in his work there until his death in 1877, and remained yet five years later—in all eight years in that country. Under his direction I did more or less work in the mountains about Rio de Janeiro for the purpose of sifting the evidence of glaciation in that region, and I am glad to say, in justice to the memory and scientific spirit of my former chief and friend, that long before his death he had entirely abandoned the theory of the glaciation of Brazil, whether general or local, and that the subject had ceased to receive further attention, even as a working hypothesis. So much for Hartt's opinions.