438 
THE GEOLOGIST. 
Mr. Mackcson, of Ilytlic, acted as the scientific tcachoi- of tlio party throughout 
the excursion. 
On arriving at the brow of the UnJcrcliff, near No. 3 Martcllo Tower, ho com- 
menced his address by explaining what was meant by the Cretaceous Formation, 
viz. : — A scries of bods distinguished by very distinct litbological characters, but 
forming a natural group when considered with reference to their fossil organic 
remains. This formation is sub-divided by geologists into, 
1. The Chalk; 
2. The Upper Grcensand ; 
3. The Gault ; 
4. The Lower Grcensand ; 
as was illustrated by a diagram, representing the section from Folkestone 
Hill to Copt Point, displaying this order and superposition of the beds. 
The Uppsr Grcensand, here very feebly represented, was first examined. In a 
■westerly direction, as at Merstham, in Surrey, and in the Isle of Wight, it forms a 
bed of considerable thickness, containing numerous fossils ; but here it appeared 
to have all but thinned out, its thickness probably not exceeding three or four 
feet, and its fossils being few and far between. 
Descending to Copt Point, that unrivalled section of the Gault with its 
numerous interesting fossils, was dilated upon ; particular attention being drawn 
to the state in which the shells of Animoiiilcs, Ilamitcs, Inocerami, &c., are there 
preserved. The estimated thickness of the Gault is about 120 or 130 feet. 
Taking up a position on the out-crop of the Lower Gi'eensand, Mr. Mackcson 
explained to the members that the history of this interesting group of sands aud 
cl.iys could not be fully entered upon, inasmuch as only the uppermost of its four 
subdivisions oifered itself to their notice within the range of the day's 
excursion. Examples of false stratification were explained, and the innu- 
merable traces of lar^e sponges on the rock-masses pointed out. The pro- 
minence of the Copt Point was due to the resistance of the Grcensand Rocks 
to the action of the waves. The junction of the Lower Grcensand and Gault, 
there visible, proved the beds to be conformable, and was the subject of numerous 
remarks, and the profusion of coniferous wood thereabduts, often bored by 
Teredos, was adduced to prove the existence of contemporaneous pine-forests, 
which must have grown on land then above the level of the ocean. 
The phosphate of lime-nodules abounding in this junction-bed are by the aid cf 
the chemist's " magic art," valuable to the agriculturist, after manufactureinto 
super-phosphate of lime. 
The existence of these nodules here was first remarked many years ago by that 
veteran geologist. Dr. Pitton ;'and in a lecture at Folkestone, in 1847, their abund- 
ance and mercantile and agricultural value was pointed out by the present editor 
of the Geologist. 
Passing along the shore in the direction of Dover, the lecturer drew the 
attention of the members to a conglomerate of shingle and lime, concreted by the 
springs tiowing from the chalk, holding carbonate of lime in solution. The 
universal use of artificial concrete at the present day gave an additional interest 
to this — Nature's own work — in which the matrix of lime was scarcely less 
indurated than tlie included pebbles of flint. 
• A halt was called near the Pelter coast-guard station, where the lecturer ex- 
plained how the beautiful underclill' extending under the white and beetling 
chalk-cliff's from Copt Point to this spot was due to the waste of the lower and 
softer beds by the sea, aud the consequent downfall of the harder supcriucumbent 
chalk-strata. 
Mr. Mackcson here threw a hasty glance at the geology of the Eas Boulonais aa 
intimately connected with that of the south-cast of England, and alluded to the 
occurrence of the true Coal-measure.s at Hardinghen, near Boulogne, thcpcssible 
continuation of which across the Channel was pointed out shortly since by Mr. II. A. 
Godwin-Austen in a most valuable paper before the Geological Society, London, and 
which proved the possible occurrence of coal at no vast depth within the area 
