APPENDIX 
314 
Table of Stratified Books — Continued 
« 
o 
I— I 
o 
CS3 
o 
pH 
P5 
O 
pH 
<1 
HH 
HH 
Ph 
Ph 
Periods, 
j 
Systems. 
Formations. 
/ 
PERMIAN or ( 
DYAS ] 
(1500 ft.) 1 
CARBONIFEROUS f 
(12,000 ft. i 
DEVONIAN & OLD 1 
RED SANDSTONE 
(5000 ft.) » 
Bed Sandstone, Marl ) Zech- 
Magnesian Limestone, etc. ( stein 
Red Sandstone and Conglomerate 
Rothliegende 
Coal Measures and Millstone Grit 
Carboniferous Limestone Series 
Upper Old Red Sandstone 
Devonian 
Lower Old Red Sandstone 
Ludlow Series 
Dominant 
type, 
Fishes 
/ 
\ 
SILURIAN ) 
(7000 ft.) j 
ORDOVICIAN j 
(15,000 ft.) 
CAMBRIAN j 
(12,000ft.) j 
Wenlock Series 
Llandovery Series 
May Hill Series 
Bala and Caradoc Series 
Llandeilo Series 
Llanvirn Series 
Arenig and Skiddaw Series 
Tremadoc Slates 
Lingula Flags 
Menevian Series 
Harlech and Longmynd Series 
Dominant 
type. In- 
vertebrates 
\ 
EOZOIC— ( 
ARCH^AN < 
(50,000 ft.) ( 
Pebidian, Arvonian, & Dimetian 
Huronian and Laurentian 
The total is 117,500 feet. Estimates in years of geological time, 
often given in Newspapers, are quite misleading. No geologist can 
say how many years ago the Eocene, or any other period, began. We 
only know that over 100,000 feet of rocks have been deposited ; and, 
by taking a rough average (1 foot in 1000 years), we get as the result 
of multiplying 100 million years. But this is only a very rough estimate. 
The world may be much older than that, it can hardly be less since 
geological time began. 
