136 Transactions of the Royal Microscopical Society. 
in perfect harmony with well-known geological facts of an entirely 
independent character, yet some at least could not have been 
established in a satisfactory manner without tasking the utmost 
powers of the microscope, which are often required to see and 
identify the extremely small or larger particles of which the rocks 
are composed. 
EXPLANATION OF PLATE CLXXIV. 
Fics. 1, 2, 3—Grains of quartz from decomposed granite. 
Fic. 4.—Grain of quartz from schist. 
Fies. 5, 6.—Grains showing the contrast between simple and complex structure 
when seen with polarized light. 
Fic. 7.—Fragment of hornblende. 
»  8.—Fragment of felspar. 
,, 9—Fragment of felspar seen with polarized light. 
, 10.—Fragment of decomposed felspar. 
,, 11.—Granule of kaolin in various positions, very highly magnified. 
,, 12.—Fragment of pumice. 
,, 13.—Grain of quartz sand from Millstone Grit. 
, 14.—Fragment of granite from the Millstone Grit. 
,, 15.—Grain of sand from the Desert. 
,, 16.—Fragment of mica schist from the slate rocks near Moffat. 
