748 THE JOURNAL OF GEOLOGY. 



mum glaciation, and on the Origin of Extra-Morainic Bowlder Clay; 

 (4) The Supposed Threefold Division of the Drift ; (5) The Direction 

 of Glaciation as ascertained by the Form of the Striae ; (6) Notes of 

 observations made in the field, with their associated references, and 

 with maps of routes and of the glaciated areas ; (7) Memoranda and 

 Brief Essays on various subjects connected with Glacial Geology ; and, 

 as appendices, (A) Extracts from the MSS. of Mr. Percy F. Kendall, 

 and (B) Field Notes in Switzerland, Italy, South Germany, Belgium, 

 and Holland. These papers and notes are presented as nearly in the 

 form in which they were left by Professor Lewis as could be done 

 consistently with a proper preparation for the press, Dr. Crosskey 

 believing that this was both wiser and more loyal to his friend than 

 any essential revision would be. 



A peculiar interest attaches to the field notes of Professor Lewis, 

 as they are thus frankly presented to us, because they open without 

 reserve the door to his inner thoughts and impressions as they arose 

 from day to day in the course of his rapid contact with new phenom- 

 ena. We are permitted to see the advances, the oscillations and the 

 occasional retreats of conviction that marked the application of his 

 dominant working hypothesis to the problems he had undertaken. 

 All who have had like experiences of oscillating conviction — and who 

 has not — will find a sympathetic chord touched in the perusal of these 

 notes. 



Professor Lewis' method was distinctively that of the working 

 hypothesis. While he entertained many supplementary hypotheses, 

 and was by no means negligent of opposing hypotheses, there was one 

 that was dominant and guided his work. The distributive affection 

 that characterizes the system of multiple working hypotheses finds 

 little expression in his investigations. With a strong faith in his 

 chosen method, he sought to disentangle the intricate drift deposits of 

 the British Isles by its energetic application. His working hypothesis 

 sprang from his previous studies. During the decade preceding his 

 notable work on the moraine of Pennsylvania, certain of the now 

 older students of the drift, east and west, had detected a series of 

 terminal moraines that had been previously overlooked or neglected, 

 and had inaugurated the morainic method of discriminating and 

 delineating the stages of glacial history. In the east the chief terminal 

 moraine lay near the limit of the drift and was, for the time, supposed 

 to be essentially coincident with it; in the west the chief moraines 



