1919] Fernald,— Ranges of Pinus and Thuja 61 
and does not cross that stream in the eastern course of its northern 
limit. It is only found about the southwestern bays of Mistassini 
Lake, from which it extends south-east, crossing the St. Lawrence 
to the westward of Seven Islands. No cedar trees were seen along 
the Manicuagan River from its mouth upward" (Low, n. s. viii. 33L). 
In regard to the region of Seven Islands, Sir William Logan tells 
us that the whole north shore of the lower St. Lawrence is Laurentian, 
* with the exception of a narrow border of Silurian strata on the strait 
of Belle Isle, another at the mouth of the Mingan River, and a third 
near the Seven Islands."! "The Manicuagan where *no cedar trees 
were seen" was explored from mouth to headwaters by Low, who 
writes “Rocks, of Archaean age alone, were met with along the vari- 
ous routes followed" (Low, l. c. 104A); but Thuja is found at the 
southern end of Lake Mistassini, for “The soil of the region about 
Lake Mistassini is made up of boulder-clay, derived from the dis- 
integration of the neighbouring rocks. . . . The finer material of the 
soil is sandy clay, with a large percentage of finely divided and inti- 
mately mixed limestone, especially [italics ours] about the southern 
and eastern shores" (Low, l. c. 69L). It is noteworthy that in his 
long canoe trip — up the Saguenay to Lake St. John, thence up the 
Mistassini River, across to Lake Mistassini and down the Rupert to 
Hudson Bay — André Michaux passed north of the southern end of 
the lake and consequently did not see this northern colony of Thuja 
at the southern end of Lake Mistassini. Writing on August 21st, 
1792, from “la Riviérre ditte Mistassin," Michaux said, “Les Thuya 
cessent au Lac [St. Jean], dit-on, et je vis pas au long de cette riv." ? 
This observation is significant for throughout its known length 
Mistassini River flows through acid country, but the northeastern, 
eastern and southeastern shores of Lake St. John are composed of 
anorthosite which, as already noted (p. 52), contains an average of 
9 % of calcium. 
Thuja is not found on the Rupert River which for its entire length 
flows over Laurentian gneiss, but it 7s found “just south of the mouth 
of the Rupert River," the eastern limit of the calcareous area already 
discussed (p. 47). Similarly it is on the lower Noddoway in the 
calcareous soils which reach south from James Bay (Bell, n. s. viii. 
80A), the region from which Pinus Banksiana is absent (see p. 46). 
1 Logan, Geol. of Canada, 47 (1863). 
2 Michaux, Journal, 1787-1796, ed. Sargent, 76 (1888). 
