21 4 Canadian Record of Science. 



geological field parties of McGill University, and a descrip- 

 tion of it, with a discussion of its origin, is now in press 

 and will appear in the Canadian Record of Science within 

 the next few weeks. The other four hills have not as yet 

 been studied in sufficient detail to enable any definite 

 statement concerning their structure to be made. 



In the Monteregian hills there are thus intrusions of 

 the nature of laccolites, true necks, and probably also 

 of stocks. The age of the intrusions cannot as yet be def- 

 initely determined. They are later than the lower Devon- 

 ian, for some of the dykes connected with Mount Royal 

 cut limestones which belong to the summit of the upper 

 Silurian, while fragments of limestone which are shown by 

 the fossils which they contain to be referable to the lowest 

 beds of the Devonian; occur as inclusions in the volcanic 

 breccia of agglomerate which is found about the flanks of 

 the same mountain. The deeply eroded character of the 

 mountains, however, shows that they are of early date, 

 and it seems most probable that the intrusion took place 

 somewhere in later Paleozoic time. 



Having considered in a general way the character of 

 the Monteregian hills as a whole, it may be of interest to 

 look somewhat more closely into the structure and petro- 

 graphical characters of one member of the group which 

 has recently been studied in some detail, namely, Mount 

 Johnson. 



MOUNT JOHNSON. 



Mount Johnson rises from the plain twenty-two miles 

 east-southeast of the city of Montreal, and six miles north- 

 east of the town of St. Johns on the Richelieu river, and 

 ^wenty-five miles north of the international boundary. 

 The little village of St. Gregoire is situated near its base. 

 The surrounding country is perfectly flat, forming a 

 fertile and well tilled agricultural district, the nearest 

 mountain being Rougemont, which lies in a north-easterly 

 direction some nine miles distant. In cross-section 

 Mount Johnson is nearly circular. (Fig. 2.) The igneous 



