220 ABSTRACTS 



the brow of the cliff which rises many hundreds of feet above the lake 

 level. All of these features must have been formed by glaciers 

 descending from the peak represented by the rim. In other words, 

 during the glacial period Crater Lake did not exist, but in its place- 

 there towered a great volcanic peak, rivaling Shasta in size, from which 

 emanated the coulees of the rim as well as the glaciers for its striation. 

 The relation of the striae to the later flows shows that the volcano was 

 yet active in the glacial period. The removal of so great a volcano 

 and the production of the large caldera is due to subsidence. This is 

 shown by the absence of a fragmental rim, such as would have been 

 formed if the material had been removed by an explosion, and also by 

 the action of the final coulee from the volcano. It flowed not only 

 over the outer slope of the rim, but also over the inner slope toward 

 the abyss into which the mountain disappeared. Since this engulf- 

 ment several smaller piles of volcanic material have been formed by 

 eruptions upon the bottom of the caldera. One of these rises so high 

 as to form an island in the lake, and furnishes an excellent example 

 of a cinder cone and lava field. 



Nipissmg-Mattawa River, the Outlet of the Nipissing Great Lakes. 

 By F. B. Taylor. 



When the waters of lakes Superior, Michigan and Huron were 

 making the Nipissing beach, their outlet was eastward over the Nipis- 

 sing pass at North Bay, Ontario, to the Ottawa valley. This outlet 

 river is called the Nipissing-Mattawa River and the three upper Great 

 Lakes of that time are called the Nipissing Great Lakes. Mr. G. K. 

 Gilbert visited North Bay in 1887, Professor G. F. Wright in 1892 and 

 the writer explored some of the ground at North Bay in 1893, and 

 more, with a visit to Mattawa, in 1895. Last autumn a canoe trip of 

 six days in fine weather was made from the head of Trout Lake to 

 Mattawa, thus covering the whole length of the Mattawa valley. 



The Nipissing beach is well developed at North Bay at an altitude 

 of about 700 feet above sea level. On the present col at North Bay 

 the old outlet bed is somewhat over a mile wide, 30 to 35 feet deep at 

 the maximum and perhaps half that on the average. The average 

 here, however, is not easy to get, for there was an archipelago on the 

 south side, and not much is known as to the number and capacity of the 

 old channels between the islands. The first swift water of the ancient 



