THE LOWER HURONIAN. 319 



have been so much altered that their true characters could be detected 

 only on careful examination. The greater the variet)^ of pebbles the more 

 difficult it becomes to conceal the true character of the conglomerate, as 

 eA^en in the most extreme cases it is probable that some one or more of the 

 kinds of pebbles ma)^ retain very nearly their normal characters. But 

 when, as was frequently found to be true, the conglomerate beds are made 

 up essentially of one kind of rock, the greenstone, and when this has been 

 metamorphosed, it is found that it is sometimes difficult to recognize the 

 original character. In fact, in such a case as this large secondary 

 hornblende crystals were found to have been produced throughout the 

 conglomerate, and in the matrix as well as in the pebbles, and likewise 

 grew from the pebbles out into the matrix. 



From Disappointment Lake north to the vicinity of Ensign Lake, 

 and from Ensign Lake east to Lake Cacaquabic, there are a number of 

 areas outlined on the map (PI. II), in which the Ogishke conglomerate 

 is exposed. In all of these areas _the conglomerate consists essentially 

 of greenstone pebbles, with granite pebbles secondary in abundance. 

 Jasper is practically wanting. In general appearance the conglom- 

 erate is green as the result of the preponderance of the greenstone, and 

 since the brilliant-red jasper pebbles are Avanting it does not present the 

 appearance of the typical Ogishke conglomerate. On the north shore of 

 Cacaquabic Lake the Ogishke conglomerate is also exposed. Here the green- 

 stone is practically the only kind of pebble in the rock, and the conglomerate 

 is very similar to some of the greenstone tuffs of other distidcts of Lake 

 Superior. It was while studying this rock that Van Hise" observed the 

 secondary enlargement of hornblende fragments. On the south shore of 

 the long east arm of Cacaquabic Lake the normal Ogishke conglomerate is 

 exposed here and there, and shows its typical characters especially well at 

 the foot of the high cliff about half a mile east of the main body of the lake. 

 Here, especiallj' on the bowlders which lie just a few inches or feet below 

 the surface of the water, the jasper pebbles, with their brilliant red color, 

 stand out conspicuously. The granite pebbles increase in quantity and, 

 as above stated, the rock is the typical Ogishke conglomerate. 



At the narrows of the lake at the center of sec. ^8, T. 65 N., R. 6 W., 

 is a phase of the Ogishke conglomerate different from those heretofore 



«Am. Jour. Sci., 3d series, Vol. XXX, 1885, pp. 2.31-235. 



