38 
AMERICAN GEOLOGY. 
the forces may act more intensely as they pass disturbing bodies, 
still the sum of the results in long periods are the same. 
In geology time is only relative. It can not be absolute, or 
at least absolute time can be reckoned only for those changes 
which have taken place in the historical period. But absolute 
time is diminutive compared with relative or geologic time. 
§ 33. It has been shown that sediments of the same age 
occupy positions which are determined in part by their size 
and weight, or the form of their particles. The large and 
heavy particles are deposited early, while the fine are trans¬ 
ported far out in the ocean. The sediments are distinguishable 
by the forms of their particles, their peculiar arrangement, or 
by the presence of fossils. Attrition rounds the salient angles, 
though it often happens that particles are consolidated while 
they are still angular. They have a foliated arrangement, 
being superimposed upon one another. This foliation has 
received the technical name of stratification. Stratification 
is manifested by folia of different kinds of matter, as sand, 
mica, and talc, or by folia of different colors. An amorphous 
mass of materials, as cart loads of sand, gravel, and stones, 
become stratified by the percolation of water when thrown 
down into heaps. Lamination closely resembles stratification: 
it is the separation of a mass into thick or thin layers by an 
imperfect or unfinished crystalization. Gneiss, mica slate, and 
talcose slate, are examples of lamination. Where the planes of 
separation are indistinct, the term sublaminated may be em¬ 
ployed. It is proper to distinguish these two forms of the 
separation of the parts of rocks. The lamination of gneiss, 
mica slate, &c., can not be regarded as a true stratification, as 
the arrangement of their parts is not due to the same causes. 
There is no evidence that the mica or feldspar planes in gneiss, 
or the mica and quartz planes in mica slate, were the result of 
a sedimentary process. Where heat has been sufficiently power¬ 
ful to fuse pebbles, it must also perfectly destroy the stratifi¬ 
cation, and the present so-called stratification of gneiss must be 
due to the heat and fusion the mass has suffered. I would 
