Page:Popular Science Monthly Volume 20.djvu/803

Rh The work, of which we have given a brief summary, "Recherches sur les Graines Fossiles Silicifiées," consists of twenty-one plates, giving accurate and exactly colored representations of the seeds examined, with careful explanations. The completion of the text was interrupted



by the death of the author, but the plates are finished, the details in them that were left lacking having been supplied by M. Renault, after comparison with the identical specimens. The whole work, in its present form, constitutes a real monument erected by pious hands to the memory of the illustrious founder of the science of fossil botany.



F all the physical features of the earth, the courses of rivers are among the most unchangeable. Once outlined, they are adhered to with a wonderful tenacity. Only a general change in the slope of their basins will usually suffice to divert them from their original courses. Mountains and plateaus may rise across their paths, but, like a saw, the river cuts its way through the obstacle. It is very rare to find a case where a river has been diverted from its course by the rising of a mountain-range or other minor elevation across it, while numberless instances of rivers having overcome such obstacles are to be seen in all mountainous regions. The Cordilleran region of the West presents us with many such examples. Many are familiar with the gorge by which Green River passes the Uintah range, in Wyoming 