38 
H. Gr. FORDHAM—ON BOULDERS 
for my purpose all the boulders which are in one dimension at 
least two feet and upwards. Of these I find there are sixteen. 
(See List I, p. 43.) -A 11 these larger boulders (except JSTos. 143 
and 150^) are worn and rounded, and have evidently been sub¬ 
jected to great wear and tear. The two boulders excepted have 
possibly been brought from Stotfold, some miles west of Ashwell. 
As to materials we find that the rock in most cases is a sandstone 
or grit, either of doubtful origin, or, in two cases at all events, 
almost certainly derived from the Millstone Grit. One specimen 
is dolerite; one appears to be part of a septaria, possibly from 
the Kimmeridge or Oxford Clay; one is a limestone, which is 
probably from the Oolitic series; and the specimens of doubtful 
origin (ISTos. 143 and 150) are a limestone and a schist. 
Considering these larger boulders alone, one is at once struck by 
the preponderance of sandstone, and it will be found that this 
material in various forms is by far the most common rock in 
our boulders of all sizes. 
On looking at the complete list of boulders and pebbles from 
Ashwell one notices the want of variety in the description of 
the materials, and, apart from the larger boulders I have enume¬ 
rated, in the size and character of the specimens. It is certainly 
the case that a large number of what may be called duplicates have 
been catalogued; but although this does in some respects cumber 
the ground, there is this point to be regarded, that in breaking 
ground in a new district, and before the characteristics of the 
boulders of such a district are thoroughly understood, it is desirable 
to make, in the first place, a more exhaustive enquiry than is 
necessary where the ground is better known. 
With this in view I have endeavoured to catalogue rather too 
many than too few, to bring together duplicates rather than omit 
any specimen of possible interest. There is also an advantage in 
this course. The collection of specimens of the boulder-rocks from 
Ashwell being as nearly as possible exhaustive, is roughly illustra¬ 
tive of the proportions of the different materials present as boulders. 
To bring out clearly these proportions I % have made a rough 
analysis of the materials; and, excluding a certain group (Hos. 
126 to 155, marked in the lists with an asterisk) which contains a 
few boulders at all events which may have come from Stotfold, and 
five others which may possibly not be boulders at all, I have a 
total of 154 remaining. Of these no less than 116, or about 75 
per cent., are sandstones and grits; 13 only are limestones, and 
there are two specimens of septaria, in all 131, or 85 per cent, of 
sedimentary rocks. Of basalts f there are 19, and of granites, 4 ; 
making 23, or 15 per cent, of igneous rocks. 
* The numbers used throughout the lists are those used to distinguish the 
specimens of the’rocks in my collection, and are used in the lists as printed in 
the British Association Beports, from which also the descriptions in the lists as 
now printed are taken. 
f I use the term basalt in a. general sense. Mr. Elsden, in his paper (see 
p. 47), goes minutely into the characteristic features of the materials of these 
boulders, and to his descriptions reference should be made. 
