156 COMPOSITION OF SOME WOOD ENCLOSED IN BASALT, 
how rapidly it must have cooled. Another interesting relic of the 
newer pliocene period that this section reveals is the trunk of a 
tree, about 2 feet in diameter, imbedded in the layer of basalt 
marked c in the above sketch. 
“The wood, though much changed, yetretains its fibrous structure 
most completely. It somewhat resembles the stringy-bark, and 
may possibly be a species of eucalyptus ; but this is difficult to 
decide without the aid of the microscope. 
“Surrounding the tree is a soft substance 2 inches thick, which 
was probably the bark.” 
bonaceous substance, but quickly burns to a pale brownish-grey 
i i graphite, 
It effervesces with acids, is fragile, and sufficiently soft to - 
scratched with the thumb-nail. 
Analysis. 
Water lost at 100° C.... iad Pier 1254 
Combined water ids ik pet eos vee “46 
NECN Naeem Ae 
35 Bombe ».2. ie ve ae ot 
Carbon ... se 514 
Iron sesquioxide 3 
», protoxide 3 
Manganese. . 
Alumina pity 
Lime 5(16-42,Ca00,) hs 
esia = 4, M co, oe 
eg a aca ca 
Soda 
Sulphur... ote ee ee des o 
Sulphuric acid... pe we owt te 
ar cacid .., a a ri on 
