: i biology and 
(above the Archean) should be based a u ERRUN of a 
- %condarily on physical structure.” Mr. : 
_ System as t unconformities, 
a “a great terrane separated from terranes above and below 4y great u: 
_ great life-breaks. or both,” AR 
l 5 mmon usag 
differs from that of his chief, as well as from the co 
But Mr. Gilbert prefers his VERR 
“own definition of a system, making it natural, and consequently 
_ and he opposes 
“any attempt to co 
he 
and shaped by th 
igi i ed over 
erce the geology of jeas oT in a rigid pity form | 
geology of another country. as ane 
As to the latter, so do all geologists; but it is x yei a i 
sition to make a matrix by combining the E E 
Countries and fitting as much as there pappen o Oa oi 
om general mould, leaving the others to comp ig ea 
He objects to the provisional color scheme o 
‘Mitte, that 
' rovision 
ems of Europe exclusively, n Sear Wana 
Hh f the earth. The geologi A 
t the systems of other parts o 
ories. 
. i f these two categorii 
- +» if they believe that «it belongs to neither o . 
; : i ining that cer- 
lhe above, to be intelligible, needs a ae UE AO 
minent geologists have lately come to t e dart of what 
— tchean should be restricted to the mee to define, and 
ub to the Present time the world has understood rt between its 
another term should be applied to the a Primordial. 
Portion, as thus defined, and the base of the 2 
