314 APPENDIX 
TABLE OF STRATIFIED Rocks—Continued 
Systems. Formations. 
Periods. 
Red Sandstone, Marl i Zech- 
PERMIAN or M 5 ; d 
DYAS agnesian Limestone, etc. § stein 
(1500 ft.) Red Sandstone and Conglomerate 
; Rothliegende ‘ 
CARBONIFEROUS { Coal Measures and Millstone Grit | Dominant 
; (12,000 ft. Carboniferous Limestone Series type, 
Lo DEVONIAN & Sy Upper Old Red Sandstone | Fishes 
S RED SANDSTONE }} Devonian 
ro) (5000 ft.) Lower Old Red Sandstone 
Ss Ludlow Series bea 
4 SILURIAN Wenlock Series 
= (7000 ft.) Llandovery Series 
oe May Hill Series 
te) Bala and Caradoc Series 
- ORDOVICIAN Llandeilo Series 
res (15,000 ft.) Llanvirn Series 
< Arenig and Skiddaw Series 
a Tremadoc Slates Dominant 
gs CAMBRIAN Lingula Flags type, In- 
eA (12,000 ft.) Menevian Series vertebrates 
Harlech and Longmynd Series 
 Bozorc— Pebidian, Arvonian, & Dimetian 
(50,000 ft.) 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. 
