by a motion that kept them in one relative position, as a plane slides over a board in the act of planing. Some of them were described as worn and scratched so plainly that there was no difficulty in pointing out which side was foremost in the act of wearing, a projecting bit of quartz or feldspar protecting the softer material behind it. In this letter he again announced his inability to account for the appearances except on the supposition that they had been enveloped in ice and moved forward over the sea bottom by currents of water. The drifting icebergs of the Labrador coast he thought might well illustrate the conditions of their production.
Perhaps it may have been because Dobson was a cotton manufacturer and not a member of one of the learned professions, or there may have been other reasons, but Hitchcock allowed the observations to pass unnoticed until 1842, when the subject was brought up by Sir Roderick Murchison in his anniversary address before the Geological Society of London.
Supported by this somewhat enthusisastic endorsement, Hitchcock then gave the letter to the public through the American Journal of Science, at the same time remarking that he had himself derived his ideas concerning the joint action of ice and water from the writings of Sir James Hall.
With this much in the way of anticipation, I will turn back to 1825 once more and refer to the writings of William Keating, mineralogist, who accompanied Major Long's expedition to the sources of the St. Peters River. This observer noted that the entire region of the present headwaters of the Winnipeek River had been at a comparatively recent period an immense lake, interspersed with innumerable barren rock islands, which had been drained by the bursting of the barriers which tided back the waters. This was plainly a recognition of the now extinct glacial Lake Agassiz.
Although the cosmogonist was fast drifting into the obscurity of the past, there were, nevertheless, occasional writers who preferred to ignore facts of observation or the efficiency of simple causes, and to seek for more difficult or more mystical methods of accounting for phenomena than those afforded by the observation of processes now in action. Thus, Benjamin Tappan, in discussing in 1828 the boulders of primitive and transition rocks found in Ohio, objected to the commonly accepted idea that such were necessarily foreign to the locality and brought by currents of water or floating ice. He frankly acknowl-
