52S OGILVIE 



proposed. 1 The following table includes the types found on the 

 Boothbay quadrangle, whose description follows. 



Table III. 



Summary of Rock Types Found on the Boothbay Quadrangle. 

 Class. Order. Rang. Subrang. Old N.ame. 



I. Persalane. 4. Britannare. 2. Toscanase 4. Lassenose Granite 



f 3. Hispanare. 3. Almerase. 4. Sitkose. Quartz-augite di- 



orite. 

 TT DnwknP I ( 4- Tonalose. Quartz-mica di- 



ll, uosaiane. _, + Austrare. 3. Tonalase. -J orite. 



( 5. Placerose. Diabase. 



L 5, Germanare \ I'. Mo^onase 6 ' 3. M^zoS.' \ Monzonite gabbro 

 ( 3 .Andase. 2. Lincolnose.*) and anorthosite. 



ITT Salfemane e Gallare \ 2 " Kilauase - 2 - Prowersose. Schist. 



111. ballemane. 5. uallare. ; 4 . Auvergnase. 3. Auvergnose. Diabase and Horn- 

 blende schist. 



V. Perfemane. 1. Maorare. 1. Dunase. 1. Dunose. Peridotite(dunite) 



In the following pages the rocks will be discussed under two 

 groups according to age. In one of these groups fall the more or 

 less metamorphosed rocks of all compositions; in the other the 

 younger rocks which according to the old nomenclature would 

 have been called diabases. The great scientific value of the new 

 system of classification becomes evident in a region such as the 

 one under discussion, where two series of rocks differing in age, 

 megascopic and microscopic characters are found to be closely 

 related in quantitative chemical characters and in the possible 

 (but not actual) proportions of certain "standard" minerals. 



The authors of the new system expressly state that meta- 

 morphic rocks are excluded from their scheme. Nevertheless, 

 in the following pages the system is applied to metamorphic 

 rocks with great significance. It is of course evident that the 

 system is not applicable in cases where there is any doubt of 

 the igneous origin, or in cases where either weathering or per- 

 colating solutions have so altered the rock that its original 

 character cannot be determined. In the types in question it 

 was always possible to determine what the original was. The * 



1 Cross, Iddings, Pirsson, Washington, Jour. Geo!., X, 1902. 



2 New name proposed in this paper. 



