Some Dykes cutting Laurentian Series. 481 



The atomic and quantivalent ratios deducible from the 

 above analysis are as follows : — 



Si 

 Ti 



610 x 4 = 2440 

 13x4= 52 



■ 2492 2492 .... 1 



Al 



192 x 3 = 576 1 



i 1 1 ho >i 



Fe m 



200 x 3 - 600 J '° J 



Fe 11 



53 x 2 = 106 : 



- 2434 .... 1 

 ► 1258 J 



Mn 



Ca 



18 x 2 = 36 

 523 x 2 = 1046 



Mg 



35 x 2 = 70 j 





Evidently the mineral belongs to the sub-species Andra 



dite 





Some Dykes Cutting the Laurentian System in the 

 Counties of Frontenac, Leeds, and Lanark, Ont. 



By W. G. Miller and R. W. Brock, Kingston, Ont. 

 [With Plate III.] 



During a canoe trip which the writers took last Sep- 

 tember in connection with a party in field geology from 

 the Kingston School of Mining, a large number of dykes 

 cutting the Laurentian series were examined. In the 

 district traversed, the county of Frontenac and adjoining 

 eastern counties, the dykes show a considerable variety in 

 mineralogical composition. It is proposed, in the present 

 paper, to give a short description of a few of the more 

 basic representatives of these. 



The larger masses of more coarsely crystalline igneous 

 rocks throughout the district belong to the granite and 

 gabbro families. The characters of the more typical 

 granites in the south-western part of the district seem 

 worthy of notice. The quartz in these generally forms 

 about one-fourth of the mass of the rock, and possesses 

 a blue colour ; the feldspar consists of microperthite, 

 orthoclase, microcline, albite, and probably anorthoclase ; 

 while the ferro-magnesian constituents, which are usually 



