The map which Prof. Geikie gives, showing the limit of ice advance during the fourth glacial epoch, seems to us open to criticism. On the ground of personal observation, the writer believes that the ice sheet of the glacial epoch here represented did not extend notably, if at all, beyond the Baltic Ridge.[18] [18] See _American Journal of Science_, May, 1887. In a recent letter, Prof. Geikie indicates that he is convinced, from subsequent personal observation, that his map is erroneous so far as the limit of the ice of this epoch is concerned. The mapping given was based on the opinion of others. Prof. Geikie is an advocate of Dr. Croll's astronomical theory of glacial climate, and thinks that even five is not the full number of glacial epochs belonging to the Pleistocene period. He believes there may have been a series of glacial epochs increasing in severity to a maximum represented by what is now designated as the second glacial epoch. This maximum was followed by a series of epochs of diminishing severity, represented by what he designates the third, fourth and fifth epochs. The essay is a timely contribution to glacial geology. =Rollin D. Salisbury.= =_Analytical Abstracts of Current Literature._=[19] [19] Abstracts in this number are prepared by Henry B. Kummel, Chas. E. Peet, J. A. Bownocker. _The Sub-Glacial Origin of Certain Eskers._ By =William Morris Davis=, Harvard University. (Proceedings of the Boston Society of Natural History, Vol. XXV., May 18, 1892). A critical discussion of the conditions under which it is conceived certain eskers and sand plateaus (plains) were formed. The Auburndale district, ten miles east of Boston, presents three classes of modified drift deposits;--sand plateaus, eskers, and kames. These deposits are well exposed. The sand plateaus have the characteristics of delta deposits of glacial streams,--even surfaces, well-bedded sands and gravels, the beds sloping outward from the "head" at an angle of 12° to 20°, and in close agreement with the slope of the plateau front, a lobate margin, deposits distinctly coarser at the head than near the front, and a series of nearly horizontal roughly cross-bedded gravels overlying the sloping beds.