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granulites, the silicates of potash and soda fuse readily and flow 
freely, and experience has proved that a mixed or double silicate 
fuses more readily and flows more freely than a simple silicate. 
Leaving this, for the present, the subject of the third essential 
constituent, that is to say Mica, must be noticed. 
The Mica contained in this Scotch granite is the dark green 
magnesian mineral, named Biotite, which is present in small 
scales in variable quantities; it is an uniaxial mica of a very 
perfect cleavage; besides the principal cleavage, there are 
indications of other cleavages to which reference alone is 
sufficient. 
Other accessory constituents are magnetite and a little iron- 
pyrite, not to mention crystallites, and needles of embryonic 
character which do not concern the present scope of remark. 
An examination of the charred and broken up granite now 
demands our attention. Concerning the degree of temperature 
to which the granite pillars could have been exposed in the 
conflagration at Newnham, only a rough approximation can be 
made; in feeling the way to this, it must be remembered, that 
the fierceness of the flames fanned by currents of wind in the 
winter month of February, and within walls which confined and 
reflected the heat from its surfaces, must have been intense, and 
must have produced effects upon the granite proportional to the 
intensity. One consideration though comes in to modify and 
qualify the judgment, namely, that the flow of heat was not a 
steady flow, but fitful and intermittent, checked by the means 
used to extinguish the fire, and by the failing supply of the 
wooden seats, fittings, etc., which soon burnt themselves out, 
' and left nothing to nourish or maintain a high temperature. 
The mean of the temperature attained may therefore be care- 
fully estimated as Black Red heat, which is a colour designation, 
and will be considered comparatively in the Appendix, on the 
colour designations of high temperatures, by eminent author- 
ities. 
The heated granite if played upon by cold water, or 
affected by cold air must have been chilled and lowered in 
temperature, producing a brittleness of condition. Fresh 
