160 ROYAL SOCIETY OF CANADA 
however, may be accounted for in the fact that throughout the Trenton 
and other outcrops on Montreal Island there may be seen at different 
elevations and horizons in the formations, intercalated sheets of lava or 
igneous materials that are interstratified between beds of limestone, etc., 
which when added together would probably account for at least a por- 
tion of the discrepancy. 
In the case of the Artesian well at the Turkish Baths which reached 
a depth of 1,540 feet (which depth would under normal conditions bring 
the drill down below the horizon of the Potsdam formation)—the drill 
does not appear to have even reached the Potsdam sandstone, the lowest 
of the Ordovician strata of the district. May it not be possible that 
during the upthrust of Mount Royal, and of the district on which Mont- 
real city is built generally, numerous crevices have been formed in 
numerous places and that the drills at Hochelaga and at the Turkish 
Baths wells have penetrated some of these very crevices in which all 
kinds of brecciated materials derived from the shearing process 
associated with volcanic materials have gathered? The nature and 
variety of the drillings in the case of the latter would almost lead one 
to arrive at such a conclusion. 
In the case of the Mooney well on Montcalm street which was pene- 
trated to a depth of 540 feet, exclusive of the covering of Pleistocene 
formations, the limestones of the Trenton and Black River appear to 
have been the only strata traversed. Considerable work remains to be 
done, however, in the Montreal district, especially in the direction of 
ascertaining the doubtful points regarding the thickness of the sub- 
jacent sediments of the Ordovician system. 
THE SILURIAN SYSTEM. 
On the south side of St. Helen’s Island, in the St. Lawrence river, 
opposite Montreal, there is exposed small patches of light-gray and at 
times rusty-weathering limestones, considerably altered in appearance, 
which upon examination are found to be fossiliferous. The fauna in- 
closed within these limestones has been studied by Sir William Dawson, 
Prof. J. T. Donald, Dr. W. E. Deeks, Dr. H. 8. Williams, and the writer, 
and reported upon in the Canadian Naturalist and Quarterly Journal 
of Science, in the Canadian Record of Science, and in the Appendix to 
Dr. Ells’s report on the south-western quarter-sheet map of the Eastern 
Townships of Quebec, Annual Report (new series) Geological Survey 
of Canada, Vol. 7, 1896, pp. 155J-156J. The fossils recorded in- 
clude some forty-five species which may be seen or studied in the Peter 
Redpath museum, where they form an important series of the Dawson 

