466 Canadian Record of Science. 



Province of Quebec. He also, however, applied the name 

 to certain more or less massive rocks associated with the 

 limestones of the Laurentian system, and of which the 

 eruptive origin is not by any means certain. 



Some gaps in the classification have lately been filled by 

 the discovery of new rocks, these have been placed in 

 their respective places in the table. Among them may be 

 mentioned lEalchite, a rock among the Diorites correspond- 

 ing to Aplite, which will be described shortly by Prof. Osann 

 in one of the Reports of the Geological Survey of Baden. 

 Also the rock described by Ramsay from Finland, under 

 the name of Polite. This latter is a coarsely crystalline 

 rock composed of eleolite, hornblende and aegerine, which 

 thus corresponds to Nepheline Basalt in the Plutonic series 

 but which also contains garnet. 



Two other very interesting rocks which have lately been 

 described are Fourchite ] and Monchiquite. - These have 

 an unindividualized base, in which are embedded pheno- 

 crysts of augite, with amphibole or biotite. In Monchi- 

 quite, olivine is also present. They therefore contain no 

 " feldspathic constituent," and might on that account seem 

 more properly to be considered as the Dyke rocks of the 

 Pryoxenite and Peridotite series. Having, however, quite 

 a different composition from these rocks, and being in no 

 way related to them, they have been classed as the Lampro- 

 phyric dyke rocks of the Theralite series, where they pro- 

 perly belong, since, judging from the chemical composition, 

 it is probable that the base would have crystalized as plagio- 

 clase and nepheline had the rock become completely crys- 

 tallized. 



It will be seen, then, that in the accompanying table the 

 Igneous rocks are first classified in three horizontal col- 

 umns, according to their structure or the depth at which 

 they have solidified, as Abyssal (Plutonic) Eocks, Dyke 



1 J. Francis Williams—" The Igneous Rocks of Arkansas," Annual Report of 

 the Geological Survey of Arkansas for 1890, vol. ii. 



- M. Hunter and H. Rosenbusch — " Tber Monchiciuite, ein Camptonitisches 

 Ganggestein aus der Gefolgschaft der Elaeolithsyenite," Tschermak's Min. und 

 Pet Mitth. xi, 1890. 



