272 Pirsson and Washington — Geology of Bed Hill, JV. H. 



hornblende, we have 92*5 and 7*5 per cents respectively, agree- 

 ing close with the calculation by measurement. The propor- 

 tions of albite, orthoclase, nephelite and sodalite must be very 

 close as given in the norm. Allowing one per cent for the 

 accessory minerals, segirite, biotite, etc., the actual mineral 

 composition is as follows : 



Accessory Minerals 1 



Orthoclase 36 



Albite 37 



Nephelite 14 



Socialite 5 



Hornblende 7 



Total 100 



Texture. — The texture of the rock is typically granitoid. 

 Outside of the accessory minerals which crystallized first and 

 therefore tend to be automorphic, the others appear to over- 

 lap. JEgirite and diopside are enclosed in hornblende. The 

 feldspars and nephelite tend to automorphism but interfere. 

 The socialite overlaps these, but is 

 distinctly the last to crystallize, fill ^^ 



ing angular interspaces between the y^^\ 



feldspars and nephelite. In one 

 specimen of the rock — that which / ; <i^.'.f^M^ 

 contained the wohlerite previously Mai 

 described — a remarkable texture 

 was observed, which may be de- ■Bljr^ 

 scribed as interdented. It is shown ^BP||§L= 

 in fig. 4 adjoining. The albite 

 lamellae of the microperthite inter- 

 growths of one crystal extend out ^IL; ^^^ 

 in optical continuity and project Fjg 4 indented texture, 

 into neighboring crystals, often en- Black, hornblende ;' white, al- 

 larging as they do so and forming bite ; shaded, orthoclase. 

 knobs or hooks. The hornblende 



does the same with the feldspar. If it were not for the 

 hornblende one might imagine this to be a secondary forma- 

 tion, albite formed by the breaking up of a soda-orthoclase. 

 The hornblende forbids this idea for it has the same structure, 

 and the writer is inclined to attribute it to local pneumatolytic 

 conditions producing a more nearly simultaneous process of 

 crystallization of all these minerals. 



Chemical Composition. — The analysis by Dr. Washington 

 of selected material from the Home quarry gave the results 

 shown in No. I of the adjoining table. 



