472 TRANSACTIONS OF SECTION C. 
In concluding this Address, I wish to express the hope that however 
incomplete the account I have given of the succession of forms may be, it will 
nevertheless help to stimulate an interest in these rock-building alge and will 
encourage geological workers in this country to turn their attention to a hitherto 
neglected group of forms of great stratigraphical importance. 
The following Papers were then read :— 
1. The Geology of the Country round Birmingham. 
By Professor C. Lapwortu, F.R.S. 
2. Notes on the Iqneous Rocks of the Birmingham District. 
By Professor W. W. Warts, I’.R.S. 
8. On the Spirorbis Iimestones of North Warwickshire. 
By Groran Barrow. 
The typical Spirorbis limestone is a rather compact rock, usually grey and 
generally containing the small fossil Spirorbis carbonartus. The number of 
these varies greatly; at times several specimens may be seen in one fragment; 
often it is difficult to find any, and, so far as experience has gone at present, 
they are never abundant in this area. Though the dominant colour is grey, 
the rock is often buff and occasionally almost white. 
The purest form of Spirorbis limestone occurs in masses of very variable 
size. The largest and most persistent bed is the Index limestone, which occurs 
roughly about 100 feet down in the Halesowen or Newcastle Group. This has 
often been confused with another and less persistent bed, lying about 100 feet 
further up and close to the base of the Keele Group. Other and less persistent 
bands haye been met within the Keele Group, notably by Mr. Cantrill. In 
addition to these distinct beds, which can often be traced for some distance at 
the outcrop, if the ground be free of drift, there are lenticles varying in length 
from a few yards to a few inches, and at times only scattered nodules. These 
smaller patches were found during the great drought, when the old marl pits 
in the Halesowen Group were completely dried up. Advantage was taken of 
this to clean the pits out, laying the rock sides bare, when these minor 
occurrences of the limestone were exposed. 
The limestones seem to have been built up of a series of films or layers, 
resulting from the evaporation of shallow sheets of lime-bearing water. When 
dried the film appears to have been cracked and more or less broken up, but 
re-cemented by later deposits of identical material; this in turn became broken 
up and re-cemented. ‘The process was repeated till a bed several feet thick was 
at last accumulated. The whole rock thus comes to have a clean sharp fracture, 
though its fragmental character is easily seen on a freshly fractured face. In 
this form, best shown by the Index limestone, there is a minimum of material 
other than lime brought into the deposit. A rough test of the brecciated 
original fragments shows the limestone to be nearly pure and containing about 
95 per cent. of carbonate of lime. 
From this we pass to the type containing small fragments of other material, 
such as marl, and the cementing matrix is not merely calcite, a considerable 
proportion of mud and sand being present. In this the lmestone fragments 
are somewhat rounded, having been transported for short distances. At times 
the fragments are locally heaped up and the bed attains a quite abnormal thick- 
ness. The band at or near the base of the Keele Group shows this character in 
the cutting in the mineral railway above Kingsbury; the fragments have been 
heaped up till it has locally attained a thickness of ten feet. 
The extreme type is really a cornstone, or a sandstone more or less crowded 
with rolled fragments of Spirorbis limestone. It is doubtful in this case if any 
of the rounded fragments are formed in siiw: the whole rock seems to have 
