BOULDER-CLAY IN LINCOLNSHIRE. 419 
rash to assert that it can only mean gravel or pebbles ; for instance, 
when it is stated that at a depth of 484 feet “shells, shingle, and 
clay” were found resting on sand, a nodule-bed with shells or selenite 
forming the base of the great mass of clay may here be indicated : 
this is merely suggested as a possibility, and as showing how en- 
tirely the geological value of the record depends on the interpretation 
of the terms and details. 
I hardly think that we have in this section a reliable basis for 
such an important theoretical superstructure as that which Mr. 
Skertchly has built upon it. It is too much to conclude, merely on 
the strength of this boring, that during the formation of the Middle 
Glacial Sands the land stood 500 feet higher than it does at present*, 
especially as the only other deep boring near Boston does not show 
a trace of such sands below the Boulder-clay, the base of which was 
reached at a depth of 1663 feet. 
It is,on the contrary, quite possible, not to say probable, that the 
greater part of the boring lies in the Kimmeridge and Oxford Clays. 
Beds of rock and sand are known to occur in and between these 
clays not far to the southward; and the isolated reef at Upware 
attests the occasional and local development of the Coral Rag. Re- 
ferring to the rock which is reported as reached at a depth of 5084 
feet, Mr. Skertchly thinks it was probably a large boulder, since it 
took four days to pierce, ‘‘ which would not have been the case had 
it been a Septaria in the Kimeridge Clay.” But a septarian con- 
cretion is not the only alternative; and this depth would probably 
be below the limit of the Kimmeridge Clay: the rock may be a 
band, like that which occurs at Elsworth, in Cambridgeshire, and 
for testimony to the hardness of which I may refer to Prof. Seeley’s 
description. Moreover another “rock” is stated to have occurred 
30 or 40 feet lower down in the section. 
Now, assuming that the lower part of the boring is in the Oolitic 
series, it becomes important to determine, if possible, the base of the 
Boulder-clay; and, in the first place, it may be noted that the boring 
at Fossdyke (only 7 miles south of Boston) reached the bottom of this 
clay at a depth of 1664 feet, passing immediately into Kimmeridge 
Clay, with septarian bands, which was bored to a further depth of 
159% feet. If we examine the account of the Boston well, we find 
that stones are repeatedly mentioned as occurring in the clay down 
to a depth of 190 feet, but that below this there is no recorded 
occurrence of stones throughout a thickness of 294 feet. All this 
portion of the section is described as ‘‘ dark clay, with shells,” ex- 
cept a band in the middle, 22 feet thick, of “light slate-coloured 
clay, with large shells.” Such a description applies far better to the 
Kimmeridge or Oxford Clay than to Boulder-clay ; for it would be 
surprising that no stones should have been met with in boring through 
a thickness of nearly 300 feet of the latter. Moreover, if we place 
the base of the Boulder-clay at 190 feet, the section then agrees 
* See ‘ Geology of the Fenland,’ p. 218. 
t Ann. & Mag. Nat. Hist. ser, 3, vol. x. p. 99. 
