Thayer Expedition.--Scientific Results of a Journey in Brazil/Geology and Physical Geography of Brazil
By L. AGASSIZ and his Travelling Companions. By , Professor of Geology in Cornell University. Boston: Fields, Osgood, & Co.
It will be seen by the title of this work that it constitutes a part of the long-expected report of the scientific results of the Thayer Expedition to Brazil. This expedition, was on all accounts the most remarkable enterprise of the kind ever undertaken in America, — indeed, considering the time occupied and the extent of country traversed, one of the most fruitful journeys ever undertaken, not excepting the great enterprises by our own and other governments. Mr. Hartt’s report on the physical geography and geology of the region studied by himself and the other assistants of Professor Agassiz may well serve to show to the public the spirit of investigation which guided, and the magnitude of the work done, by the gentlemen who co-operated in this investigation of the great empire of the South.
His work being a part of a series of reports on the same region, Mr. Hartt has evidently felt himself limited in the scope of his treatise to the range of subjects properly falling under this title. This takes away from the book the general interest which would naturally be attached to a journey by a careful observer in the ever-new tropical region of South America. The book lias few of those traits which will make it popular in the worse sense of that word. It differs entirely from the class of books to which, for instance, the “Brazil and the Brazilians” belongs, and though it may want the few good traits of that eminently popular volume, it wants equally its many bad characteristics. A glance at the table of contents shows at once that it is as a scientific report that the volume is to be considered, though the matters of which it treats, as well as the methods in which they are considered, makes it interesting even to the unscientific student of South America. Although Mr. Hartt’s observations extend over only a small part of the whole surface of the Empire of Brazil, they have covered by far the larger part of the coast line of that region, and extended far enough into the interior to give us a great deal of information about the most important commercial provinces, those containing the diamond districts of Diamantina, Chapada, Sincora, etc., and the extensive coal basins whose development is to play so large a part in the future of the continent.
Beginning with the province of Rio Janeiro, Mr. Hartt takes up the several other provinces, and gives a succinct description of each, drawn from his own note-books on from the journals of his fellow-travellers, compared with and illustrated by the work of other observers in the same region. We cannot follow him through the encyclopædic detail of this part of his work. The last chapter contains the only important generalizations which his book affords, for during the first eighteen chapters our author sticks very closely to his facts. Some of these general conclusions are of the highest value. Mr. Hartt seems to have satisfied himself that the gneissic rocks of the province of Rio de Janeiro and the Serra do Mar are of Laurentian age, and that they were lifted above the sea as early as the beginning of the Palæozoic time. While acknowledging the probability of these two conjectures, we must confess that the evidence does not warrant us in the supposition that these opinions are to be admitted into the facts of the science without further evidence. The admirable criticism levelled against the hasty conclusions of geologists, in the chapter on “ Illogical Geology,” by Mr. Spencer, should make that class of naturalists see the dangers involved in this sort of reasoning. It must be confessed, however, that Mr. Hartt’s opinion concerning the age of these rocks receives striking confirmation from the parallelism between the lithological and mineralogical features of the materials of which they are composed and rocks from the Laurent-ian system in this country. This comparison has been made by Dr. T. Sterry Hunt, whose opinion on such points is of the highest value.
Unquestionably the most important matter discussed by Mr. Hartt concerns the evidences of glacial action in the region from Rio to the Amazon. When Professor Agassiz, in 1865, first announced the existence of glacial drift in the neighborhood of the equator, the scientific world pretty generally believed that the judgment was hasty ; that it was too much influenced by a desire to extend the domain of that geological agent, of which he had been to a singular degree the discoverer, to regions where it would seem impossible for it to have operated. We hope the clear statements of Professor Hartt will at least give pause to the illogical talk of those who, ignorant of the facts, have in a very unscientific way hastened to protest against Agassiz’s conclusions. Mr. Hartt tells us distinctly that he was at the outset opposed to the view of his master (and of his complete scientific independence the writer can testify), that he conceived it to be in the highest degree improbable that ice could have worked in Brazil as it has worked in British America. Yet he has by careful study been drawn to believe that the whole of the shore region of Brazil was, during the last geological period, covered with ice to a great depth, which performed then precisely the same part which it performed probably at the same time in North America. We cannot give Mr. Hartt’s argument in detail ; it is, however, convincing to any right-minded man that further objections to Agassiz’s view must come from persons who have studied the facts at least as carefully as he and Mr. Hartt have done.
The same good reasons which would deter the critic from criticising the style of a “blue book” might be urged against carping about the rhetorical shape of Mr. Hartt’s book. There is so little, however, to be said against the way in which the author has presented the matters of which he treats, that we may, without risk of prejudice to him, say that he has considered clearness of statement very much more than elegance of diction ; that he is laconic to the extreme of being dry. The reader meets so many full - points in the Course of a page, that he feels as if he were travelling over an intellectual corduroy road. But the worst form of this offence is something venial compared with the sin of fine writing.
Of the work as a whole it is not too much to say that it is the most valuable contribution yet made towards the development of the physical history of the noble Empire of Brazil. It was the great good fortune of the Thayer Expedition that it secured the earnest and intelligent co-operation of the most enlightened of modern sovereigns, Don Pedro II. We are heartily glad that this important event in the exploration of his country should have come from the energy and talent of our own. South America may or may not come to be the home of the emigrants from its overcrowded sister continent in the last decades of the next century, but it is certainly the fairest field now open to the exploring ambition of our American students who long for uncultivated fields. We hope there may be many to follow the way in which Mr. Hartt has. led.