122 
THE CLASSIFICATION OF* THE TERTIARY 
DEPOSITS. 
By Prof. JOHN W. JUDD, F.R.S., Sec. G.S., &c. 
T HERE are probably few achievements of genius which will 
bear comparison with William Smith’s famous discovery of 
the true order of succession among the British stratified rocks. 
Whether we regard the state of knowledge upon the subject at 
the time when he commenced his labours, or consider how few 
are the changes which have been introduced into his scheme of 
classification by the work of subsequent observers, we shall be 
equally convinced of the justice of his claim to rank as ‘the 
Father of English Geology.’ 
In his original table, drawn up in 1799, William Smith 
divided the British strata into twenty- three groups ; the highest 
being the Chalk and the lowest the Coal. And though in sub- 
sequent tables he introduced both older and younger formations 
than these, it is evident that the series of deposits of which the 
order of succession was perfectly made out by him, embraced 
only the strata from the Carboniferous to the Cretaceous rocks 
inclusive. Thus, in 1815, Smith grouped all beds below the 
Mountain Limestone as Red Rhab, Dunstone, Killas, and Slate, 
while those above the Upper Chalk are classed in upward 
succession, as 1, Sand ; 2, Crag ; 3, Sand ; and 4, London Clay. 
It remained, therefore, for William Smith’s successors to 
complete his work, by classifying, on the principles which 
he had laid down, the strata which are older than the Carbo- 
niferous and those which are younger than the Cretaceous. 
With respect to the former, the labours of Sedgwick, Mur- 
chison, and Lonsdale, left little to be desired, and the result of 
these labours was the establishment of the Cambrian, Silurian, 
and Devonian systems. The distinguished founders of the 
Pala30zoic classification followed William Smith’s method of 
determining the order of succession among strata, which con- 
