E. MINERALOGY AND GEOLOGY. 239 



of marine animals found above the level of high-tide mark; 

 the presence of extensive stratified deposits, at points where 

 fresh-water lakes could have had nothing to do with their 

 formation ; and the existence of a characteristic topography 

 not explicable on any other supposition than that of marine 

 action. In his investigation of the coast of Maine, Professor 

 Shaler has not been able to rely to any great extent upon 

 the first of these three natural indications ; the evidence af- 

 forded by the extensive stratified deposits has been to him 

 the most important, both in its nature and its quantity. 

 Taking the masses of stratified drift as the only acceptable 

 and abundant proof of depression, he considers that we must 

 look at the question of the origin of these bodies of drift and 

 the possibility of their being formed by other agents than 

 those which are at work in the sea. Some slight amount of 

 stratification seems not inconsistent with the theory of the 

 action of water in the formation of extensive sheets of drift; 

 but when the stratified drift is distributed in extensive sheets 

 along the shore, all doubt of marine action may be fairly put 

 away. 



The neighborhood of Boston, like the whole country south- 

 ward to New York, is characterized by having a vast accu- 

 mulation of drift materials disposed in four distinct forma- 

 tions, each indicating a separate stage of the glacier period; 

 namely, first, massive drift in patches, which are the frag- 

 ments of a great body of drift of great thickness left by the 

 old glacier ice-sheets. This drift is quite without traces of 

 stratification, and a large part of its pebbles are scarred by 

 glacier scratches. Second, bodies of glacier material rudely 

 distributed by water, the glacier scratches generally worn 

 away from the surface of the pebbles, the whole indicating 

 one or more of the processes by which the re-elevation of the 

 country was effected after the passage of the glacier ice. 

 Third, a secondary glacier series, indicating the recurrence 

 of local depressions after the partial re-elevation of the coun- 

 try. These secondary glaciers in the neighborhood of Boston 

 occupy only the larger stream-beds. Fourth, the rearranged 

 beds lying within a few feet of the present level, which indi- 

 cate a long-continued rest of the sea, at or near its present 

 place. At this level the life -bearing bodies of drift come 

 again into prominence. Fifth, the extensive mud-beds and 



