98 Lieut. Baddeley on the geognosy 
which it has been used. This term, wherever it may ap- 
pear in this essay, is meant toimply any rock in which horn- 
blende predominates, without any regard or reference to those 
theoretical notions which it has been often used to convey. It 
here more particularly means an aggregate composed of black 
crystalline hornblende, small grey crystals (or rather scales 
composed of an assemblage of crystals) of felspar and a little 
unelastic mjca or talc: in short, a substance similar to what has 
been before described as associated with the white marble at 
Moulin a Baude, but essentially differing from it in the manner in 
which it occurs. It much resembles also a compound that is 
found on the Montreal Mountain, to which a volcanic origin has 
been ascribed. The granite with the trap here associated was 
of a greyish color. In it we in one place observed nodules of 
magnetic iron, exhibiting a very iridescent surface resembling 
some ores of copper, for one of which it was at first mistaken. 
This ore is very strongly magnetic, apparently as much so as 
maleable iron. Contrary to the hornblendic compound in the 
gneiss at Moulin a Baude, it is not easy to procure a fragment 
of this trap shewing the two rocks in contact, as upon being 
struck they separate immediately and it is then perceived that 
the trap has externally that smooth even surface which a mould 
bestows on the substance cast in it, shewing generally no ap- 
pearance of entanglement or conglomeration at the places of con- 
tact. On the weathered surface of the trap the felspar is of- 
ten brown and prominent. This trap is often very magnetic. 
The granite of La Boule, for such we call the rock though 
apparently stratified, is composed of grey quartz, reddish fel- 
spar and small points of brown mica. A little above the 
line of junction of the river and the rock and on its south- 
eastern side, a thick dyke of trap traverses it nearly horizon- 
tally and at right angles to the stratification. It appears to 
rise out of the water at the western extremity of La Boule, 
and 
