662 
DESCRIPTION OF THE MAPS IN VOL. I. 
Nor can we, without becoming prolix, enter into much further explanation of the General Map. 
Three points in it, however, seem to require notice. The first is, that it indicates 
a clear distinction between those sedimentary (azoic) strata («) which preceded all traces 
of animal life, and those palaeozoic deposits (I, 2, 3, 4) which are charged with organic 
remains ; each member of this vast group being specially distinguished. 
The second point is, that whilst the Tertiary series is designated by three colours, which on the 
whole stand for the Eocene 1 , Miocene and Pliocene periods, the latter is specially repre- 
sented in South-eastern Russia and the adjacent Asiatic countries, by the remains of a 
vast internal brackish sea, as large as or larger than the present Mediterranean, which must 
have been almost entirely separated from the ocean. (See p. 652.) 
In defining the outlines of the deposits of this vast former Mediterranean, we have been 
guided by what we know of it from personal observation in the steppes of the Kirghis, 
between Orenburg and Astrakhan, and in the tracts adjacent to the Sea of Azof, the 
Crimaea and the Black Sea. In those districts we clearly distinguished limestones which 
had been elevated to 150 or 200 feet above the sea, from sandy, low steppes, in which 
most of the same Caspian remains exist, and we have therefore endeavoured to carry out 
such division, by employing two tints of the same colour in reference to far and distant 
tracts of which we have no personal knowledge, but which from the description of various 
travellers mentioned in the work are believed to be of the same composition. The darkest 
of these tints (fig. 10) represents the bottoms of the earliest Caspian which have been 
elevated into rocky promontories, and the lighter tint (10') the bottoms of the same sea 
subsequently desiccated, and of which the present Aral and Caspian are the greatly dimi- 
nished existing types. (The northern raised sea-bottoms are similarly marked 10'.) 
Thirdly, in reference to the very striking phenomenon of the distribution of the Scandinavian 
drift, we have indicated by arrows that it proceeded excentrically from a common central 
region, and have marked by an engraved devious line (coloured red) the extreme points to 
which the erratic blocks have been transported southwards and eastwards. 
Lastly, notwithstanding the imperfections which must pertain to the first geological maps of 
such vast and slightly explored regions, we trust that our endeavours to extend the newest 
British classification into Asia, and thus to co-ordinate large portions of the globe, will be 
adequately appreciated by those who are aware of the difficulties we have had to en- 
counter, and the importance of the objects in view. In truth, the region we have ventured 
(perhaps too boldly) to illustrate, is nearly twice as large as all those portions of Europe 
hitherto described by geologists ; and this fact alone must be our apology for inevitable 
inaccuracies of detail, particularly in reference to the countries which surround the area of 
our personal explorations. In conclusion we would merely say, that if the principle of 
geological arrangement be found correct, our great object is accomplished. 
See Appendix, p. 651. 
