9 
covered continuance of the great plainof Northern Europe must 
have sunk down under the existing seas, and been again brought 
up by a slow elevation nearly to the present low water-mark. 
Since then there has been a slight depression of the British Isles 
of 20 or 25 feet, causing the raised beaches and inland sea-cliffs 
which are found along our shores, followed by a slight elevation 
which has brought sea and land to their present level. 
CHANGES IN BRITAIN. 
Now here comes in the value of the historical standard on which 
I commented at the commencement of this essay. It is certain 
that all those movements in Britain have been prior to the Roman 
period and to the time when tin was carted at low water across 
the spit connecting St. Michael’s Mount with Cornwall, to traftic 
with Pheenician merchants. And what is more important, it is 
certain that where we have authentic records, as in Egypt and 
Chaldea, no change has taken place in the physical geography, 
the levels of sea and land, the climate, or the fauna for 7,000 
years, and that these countries were then the seats of populous 
and civilized empires, with the types of the principal races of the 
human family and their distinctive languages, already firmly 
established. This is of itself a conclusive answer to those who 
invoke recent deluges and cataclysms, or otherwise attempt to 
compress the post-glacial period within such a limit as 8,000 or 
10,000 years. Its actual duration can only be estimated from a 
careful and minute investigation of the changes, such as those 
above enumerated, which have actually occurred since the deposi- 
tion of the latest boulder-clay, and of the time they must have 
required, starting from the fact that 7,000 years in Egypt and 
Chaldea, have been insufficient to make any marked change in 
existing conditions. Such an estimate has been exhaustively 
made by Mr. Mellard Read, of the Geological Survey, one of our 
best authorities on post-glacial geology, from the numerous pits 
and borings sunk in the valley system of the Mersey, and his 
conclusion is that 60,000 years is a probable estimate of the time 
required, a date which fits in remarkably well with that assigned 
by Croll, Geikie, and Wallace, from the combination of geological 
and astronomical causes to which they assign the vicissitudes of 
the glacial period, 
Tse Vast ANTIQUITY OF THE HuMmAN Race. 
It is, however, from the glacial and inter-glacial periods that we 
gather the most striking proofs of the enormous antiquity of the 
human race. I need not refer at any length to the discoveries of 
what may be called the Boucher-de-Perthes period of paleontologi- 
cal science, which have firmly established the fact that almost 
everywhere throughout the old and new worlds rude human im- 
plements, connected with remains of extinct animals, have been 
