Marcou.] 
358 
[Noy. 6, 
Delesse, Daubree, Barrande, Capillini and myself and many other 
geologists who agree with us, do not know quartzite from gneiss? 
Now that I have answered as briefly as Mr. Selwyn wished me 
to do, I shall leave it to the geologists to judge of the merits of the 
question of the so-called “ Laurentian gneiss” of the Fall of 
Montmorency. 
In 1861, on my second visit to Montmorency, wishing to see why 
Logan continued to call the beautiful quartzite which forms the 
bed of the Montmorency river, the chasm of the precipice and the 
foot of the fall “ Laurentian gneiss,” I took special care to ob- 
serve very closely the rocks and brought away with me specimens 
taken in situ at different places, choosing specimens to illustrate 
the average structure and composition of the rocks, in order to sub- 
mit them to other practical geologists well informed on lithology, 
being unwilling to rely entirely upon myself. I first showed my 
specimens ;to Dr. Charles T. Jackson of Boston, who declared that 
they were quartzites. When in Paris in 1866, I showed them 
to Delesse who called them quartzites, and afterwards to Bar- 
rande and Daubree who said, “ pure quartzites.” Prof. G-. Capel- 
lini of Bologna also visited the Montmorency fall in 1863 and pub- 
lished a description with a section of the fall (see Ricordi di un 
viaggio scientifico riell* America settentrionale, p. 55, Bologna, 
1867), in which he refers the rocks of the fall and river bed near 
the precipice to the quartzites. 
Mr. Selwyn, in his correspondence with me, insisted that the 
rocks were gneiss. I asked him to collect in situ at different places 
of the fall several specimens and to send them to Mr. M. E Wads- 
worth, Director of the Michigan School of Mines, the best expert 
in lithology in America, adding that I would accept his determi- 
nation. Mr. Selwyn has made no answer to my proposal. 
If Mr. Selwyn is truly desirous of settling the lithological ques- 
tion of the composition of the rocks forming the Fall of Montmo- 
rency, I hope he will be induced to send specimens to Prof. H. S. 
note with Barrande (“ The primordial fauna and the Taconic>ystem > ’ in Proceed. Bos- 
ton Soo. Nat. Hist., 1860), in which I call the rock forming the fall, quartzite , from 
notes taken in Sept., 1849, when visiting Montmorency, Logan chose to disregard my 
determination of the rocks and continued in all his numerous publications on the fall 
of Montmorency, to call the rocks gneiss. Mr. Selwyn has done the same, publishing 
a section of Montmorency fall as late as 1884, in which he refers the rocks forming the 
fall to gneiss. So with Logan and Mr. Selwyn: the determination of the quartzite of 
Montmorency fall, as “Laurentian gneiss,” is made with the full knowledge of the 
different opinions of other practical geologists. 
