THE CRETACEOUS ROCKS OF BRITAIN. 
1 
4 * 
country along the course of this horizon revealed the fact that these 
rocky beds were continuous and constant in character, and as they 
were well exposed in quarries near Melbourn, between Cambridge 
and Royston, they were named Melbourn Rock after that village. 
As the horizons of the ChalkRock, Melbourn Rock, and Totternhoe 
Stone were all capable of being traced across the country and indi¬ 
cated by lines on the map, it seemed to us at first that the Chalk 
might be divided into four parts or stages. When, however, fossils 
had been carefully collected by Mr. Allen from all the pits found 
during our survey it became evident that the Totternhoe Stone was 
only a lithological variety of the Lower Chalk, while the Melbourn 
Rock and the Chalk Rock separated well marked palaeontological 
divisions of the Chalk. 
The results of our examinations of the Cambridge Chalk, therefore, 
entirely agreed with those arrived at by Dr. Barrois, both with 
regard to the general succession of zones and the grouping of these 
zones into three stages. In other words, we made it clear that this 
Chalk was naturally divided into Upper, Middle, and Lower portions, 
and we demonstrated the possibility of drawing the boundary 
lines of these divisions on a geological map. 
During the survey of part of East Lincolnshire from 1879 
to 1883 I found that the Chalk of that county fell naturally into two 
divisions, which corresponded generally with the Lower and Middle 
Chalk of Cambridgeshire, and were divided by a set of hard rocky 
beds, which appeared to include a representative of the Melbourn 
Rock.* This conclusion was confirmed by the subsequent investi¬ 
gation of Mr. W. Hill, who also found the same divisions extend 
through the Chalk of Yorkshire.f 
Meantime (in 1886), Mr. W. Hill and the author traced the zonal 
divisions of the Cambridge Chalk northward through Suffolk and 
Norfolk to Hunstanton, and described the gradual lithological 
changes which take place along this line of country.^ 
Since the year 1884 the author has been engaged in collecting 
materials for the present Memoir, and in drawing the boundary 
lines of the Lower, Middle, and Upper Chalk through the counties 
of Hertford, Bedford, Buckingham, Oxford, Berks, South Wilts, 
Dorset, and Devon ; the result being to prove the continuity of the 
Melbourn Rock and the Chalk Rock throughout these counties, 
except in Devonshire, where they lose their special characters. 
The same divisions have been mapped in North Wilts and Hamp¬ 
shire by Messrs. F. J. Bennett and C. E. Hawkins, through Sussex 
by Mr. Clement Reid, and in the Isle of Wight by Mr. A. Strahan. 
The equivalents of the Melbourn Rock and the Chalk Rock were 
* See The Geology of part of East Lincolnshire, Mem. Geol. Survey, 
1887, p. 28, 
f Quart. Journ. Geol. Soc., Vdl. xliv. p. 320, 1888. 
X Quart. Journ. Geol. Soe., Vol, xliii. p. 544, 1887. 
