26 



present know titaniferous, tlie percentage of titanium being as a general 

 rule too high to permit of them being employed for the production of 

 iron. 



In the Geology of Canada published in 1863, Sir William Logan 

 gives as the result of his stndy of the Laurentian system in the Gren- 

 ville region the following section through the series, arranged in 

 ascending order : — 



feet. 



1. Orthoclase Gneiss of Trembling Mountain, probably exceeding 5,000 



2. Trembling Lake limestone 1,500 



3: 2nd Orthoclase Gneiss 4,000 



4. Green Lake limestone with bands of gneiss and garnet rock 2,500 



5. 3rd Orthoclase Gneiss 3,500 



6. Grenville limestone with bands of gneiss 750 



7. 4th Ortlioclase Gneiss , 1,580 



8. Proctor's Lake limestone 20. 



9. 5th Orthoclase Gneiss, passing into anorthosite 3,400 



iO. Anorthosite, thickness wholly conjectural 10,000 



32,250 

 Mr. H. G. Vennor, who, while connected with our Geological 

 Survey, studied these rocks for many years, commencing his investiga- 

 tions in the district about Hastings County, Ontario, and continuing 

 them northward across the Ottawa into Ottawa County, and who als^ 

 studied them in the anorthosite area north of Montreal, has recently 

 given to Dr. Selwyn a condensed statement of the results of his 

 investigations. He divides the Laurentian system into three sub- 

 divisions. The lowest of these, which he calls Division .4, is a great 

 mass of syenitic gneiss, generally deep red in colour and is destitute of 

 crystalline limestones and mineral deposits. This probably is equivalent 

 to the lowest or Trembling Mountain gneiss of Sir William Logan's 

 section. Following this in ascending order is a series of hornblendic 

 and pyroxenic I'ocks, diorites, anorthosites, etc., constituting his Divi- 

 sion B, and which is in its turn overlayed by another series of gneisses, 

 which, however, are associated with numerous bands of crystalline 

 limestone, and contains great deposits of graphite, apatite and ii'on ore. 

 Mr. Vennor believes Divisions £ and C to be comformable to one 

 another and to overlie Division A unconformably. Division B and C 

 form but a small portion of the whole series and occur merely as a 



