220 Canadian Record of Science. 



the apatite having a very irregular outline, while in cases 

 where a foot-wall was supposed to exist this was found to 

 be due to the presence of a cross-dyke. The hanging-wall 

 where reported consisted in most cases of the edges of the 

 gneiss, the planes of stratification in some cases meeting 

 the apatite bearing portion of the dyke at very consider- 

 able angle. 



An important feature was observed at several of the 

 mines, tending to show that subsequent intrusions of dior- 

 itic or doloritic rock have apparently exercised a marked 

 influence upon the occurrence of apatite in workable 

 quantity. Thus at the Etna mine a large dyke of pyroxene, 

 which extends in a southwest direction towards the Emerald 

 mine and on the prolongation of which the latter is pos- 

 sibly situated, is intersected nearly at right angles by a 

 heavy dyke of dolerite. Along the line of contact con- 

 siderable quantities of iron pyrites have been developed, 

 and the apatite which has been mined at this place to a 

 depth of not far from 200 feet is found in that portion of 

 the pyroxene adjacent to the dolerite intrusion, along which 

 the workable deposit of phosphate apparently extends. A 

 somewhat similar occurrence in the case of mica was ob- 

 served at the Clemow & Powell mine in the Township of 

 Hincks, where the main mass of pyroxene which intersects 

 crystalline limestone is in turn cut across by a dyke of 

 syenitic rock, principally composed of feldspar and quartz, 

 alongside of which great masses of mica crystals, often of 

 very large size, have developed in the pyroxene. This 

 feature of mica and apatite occurring as the apparent result 

 of a second intrusion, has been also noticed at other points, 

 both in the Gatineau and Lievre districts. 



With regard to the age of the different intrusions, the 

 apatite bearing pyroxene appears to be the oldest. In- 

 stances, as already noted, are frequent where this is 

 clearly broken across by dykes of feldspar and syenite, 

 which have been in turn cut by trappean rock. Other 

 syenite masses are apparently of more recent date than 

 the trap dykes, as these are in several cases observed to be 



