Vol. 4] Thelen. — Thermal Conductivities of Certain Schists. 225 



The quartz is very abundant. It occurs in small grains whose 

 angular character is well brought out by the stepping of the 

 interference colors. It is full of dark spots and fine inclusions 

 the latter largely apatite. Feldspars are very rare. A few ortho- 

 clases and acid pla^ioclases were found. 



Apatite occurs plentifully, both as inclusions in quartz and 

 as fairly large crystals between the quartzes. 



The magnetite is very plentiful in small grains, usually asso- 

 ciated with decomposed micas. Pyrite occurs irregularly. In 

 a few places half of the field is pyrite. It seems here to be occu- 

 pying the place of micas too, though the latter contain no sul- 

 phur. Hematite and titanite occur rarely. A few large sections 

 of clinochlore were found. 



The axes of the wax figures gave results of 1.000: .894: .715. 

 It is manifestly impossible to tie these results down numerically 

 to the known thermal conductivities of the constituent minerals. 

 The undulatory fracture indicates that no results of any value 

 for our work can be obtained. The presence of small garnets 

 and local impoverishments due to their formation points in the 

 same direction. The numerical results checked more poorly than 



for any other rock, necessitating the reading of several dozen 

 ellipses on one face to get the probable error. Thus (fig. 10) read- 

 ings on the face y reduced to 100 : 79.7 for A : y ; and on the face 

 x reduced to 100: 86.9 for A: x. But on the face perpendicular 

 to A the values were 100 : 80.8 for B.C. If we construct an 



