Miles and 
Kilometres. 
77 Or 11): 
284 km. 
180 m. 
290 km. 
EO4. 1 m. 
295 km. 
185.1 m. 
296 km. 
109 
where the dip rises to 75°. Excellent exposures 
of flat-lying Trenton limestone are to be seen on 
both sides of the railroad in the vicinity of Hull. 
From these limestones, which have a total thick- 
ness of about 600 feet (183 m.), more than 50 
species of fossils have been recorded, including 
Plectambonites sericeus, Sowerby, Pachydictya 
acuta, Dekay, Zygospira recurvirostris, Hall, 
and others. 
The faulted northern boundary of the Tren- 
ton, where it abuts against beds of the Chazy 
series, is not exposed, being covered by a heavy 
deposit of Leda clay. This conjunction of clay 
and limestone, both of a high degree of purity, 
is as advantageous for the production of cement 
as any in the country. The large plant of the 
Canada Cement Co. testifies to these propitious 
geological conditions. Extensive quarries for 
building stone, lime and cement have also been 
opened in the Trenton limestone. 
Maniwaki Junction— 
Ironsides—Alt. 182 ft. (55.3 m.). The Chazy, 
Calciferous and Potsdam formations appear 
in that order toward the north, the Potsdam 
resting unconformably on the Pre-Cambrian. 
All of these formations and their faulted west- 
ern contact with the Pre-Cambrian, are covered 
along the Gatineau Valley railway by Leda clay 
which is in turn covered by Saxicava sand, 
though in places this has been subsequently 
removed, as for example between Maniwaki 
Junction and Chelsea. 
Chelsea—Alt. 365 ft. (110.6 m.). Immediate- 
ly north of Chelsea station the first exposures of 
Pre-Cambrian are found. On the east side of 
the track is a richly garnetiferous gneiss with ver- 
tical banding, which is cut by pegmatite veins. 
Grenville limestone intruded by binary 
granite and mica diorite is exposed in a cutting 
at this point. The limestone is in highly 
inclined or contorted bands of various thick- 
nesses. Further north the limestone is followed 
by more exposures of binary granite. 
