GEOLOGY OP FRANKLIN COUNTY 95 



has not been thoroughly traversed in the first place, and more- 

 over the rocks are readily eroded and show only meager ly in out- 

 crop. Three of the patches indicated on the map may have 

 .greater extent than there shown, as they are in line with areas of 

 little relief in which no outcrops could be discovered. 



The Franklin Falls, Saranac village and Follensby pond 

 patches constitute the more southerly of the two northeast and 

 southwest belts previously mentioned. Jt will be seen from the 

 map that the depression occupied by Lower and Middle Saranac 

 lakes (the latter usually called Bound lake) is on the same line 

 and with the same trend. Since no rock save anorthosite is ex- 

 posed along these lakes, and the exposures are practically con- 

 tinuous around the shores, with numerous islands of the same 

 rock, this concordance in trend may be a mere coincidence, but it 

 at least suggests strongly that the depression may have been 

 initiated by the presence of a continuous belt of the Grenville 



Tocks along this line. 



Doubtful gneisses 



Rocks which must be referred to this group are exposed pretty 

 continuously across the county from east to west, in the northern 

 part of the Precambrian area, and as found near the Potsdam 

 Doundary have been briefly described in a preceding report. 1 

 Hocks differing widely in character, and not improbably consider- 

 ably in age, are included in this category, which, as at present 

 used, serves as a convenient receptacle in which to place all 

 .gneisses whose origin and relations are undetermined. In other 

 words it is a temporary expedient in mapping, made necessary by 

 the difficult character of the region. It is quite certain that, as 

 present mapped, many small areas of the later granite are in- 

 cluded, the term later being made use of simply to express the 

 possibility of there having been two periods of granite intrusion, 

 the earlier representatives being more gneissoid than the later. 

 'These areas are too small and with too indefinite boundaries to 

 appear on a small scale map. On the assumption that these 

 rgneisses are of igneous origin, they are readily separated into 



lCushing H. P. 16th an. rep't N. Y. state geologist. 1896. p. 16-21. 



