646 POPULAR SCIENCE MONTHLY. 



many varieties occur there. Attention is especially called to the 

 liability of mistaking flow structure for stratification, the similari- 

 ties and differences being explained. At Marblehead Neck, also, 

 a careful study is made of the formation of pebbles, all stages being 

 shown from the dislodging of fragments from the cliffs by frost 

 action, the dropping into reach of the waves, the first rounding of 

 the sharp angles to the subangular outline, and finally the round- 

 ing of the fragment into a complete pebble form. 



At Newton Centre a study of contemporaneous beds is made, in- 

 cluding their relations to the inclosing rocks and a comparison of 

 their characteristics with those of intrusive beds. 



Eruptive masses, metamorphic rocks, and vein phenomena are 

 all well shown at Fitchburg, where Rollstone Hill is an eruptive 

 mass of granite cutting through the metamorphic mica schists and 

 gneisses, and the granite in turn is cut by very numerous veins of 

 pegmatite, abundantly rich in tourmaline crystals and occasionally 

 having beryl. 



Glacial structures are next taken up. At Newtonville is studied 

 the esker and sand plateau, rendered famous by the work of Prof. 

 W. M. Davis and others; at Clinton an exceptionally fine set of ter- 

 races, and the best example of roclies moutonnees near Boston, where 

 a class can be taught in a very few minutes to recognize that the 

 movement of the ice sheet must have been from the north toward 

 the south; and at Stow and Haverhill are studied drumlins. 



After this, special attention is devoted to the subsequent struc- 

 tures of rocks, such as folds, faults, cleavage, joints, etc. Typical 

 places, as before, are selected for each, and the work carried on 

 in the same manner. When this course has been entirely accom- 

 plished, then places of greater complexity and where the problems 

 are not quite so plain are visited, and opportunity is given to exer- 

 cise the skill or knowledge already gained. 



Following this, a series of lessons is devoted to the study of 

 typical places illustrating the various historical strata occurring in 

 Massachusetts; among others, Nahant and Braintree for the Cam- 

 brian, Attleboro for the Carboniferous, Mount Holyoke for the Tri- 

 assic, Gay Head for the Cretaceous and Tertiary, Rockport, Mar- 

 tha's Vineyard, and claypits of Cambridge for the Glacial Cham- 

 plain. 



The work in this course has been marked by enthusiasm, and the 

 attendance has been very large, reaching a maximum of two hundred 

 and ten, with an average attendance of seventy-one in the autumn 

 of 1896. As a direct outcome of this work, and connected with it, 

 several excursions to distant points have been made by parties under 

 the charge of Professor Barton during the summer vacations. The 



