340 REPORT—1890. 
Eighteenth Report of the Committee, consisting of Professor PREst- 
wicu, Dr. H. W. Crosskey, Professors W. Boyp Dawkins, T. 
McKenny Huaues, and T. G. Bonney, and Messrs. C. E. 
De Rance, W. PENGELLY, J. PLant, and R. H. TIDDEMAN, 
appointed for the purpose of recording the Position, Height 
above the Sea, Lithological Characters, Size, and Origin of 
the Erratic Blocks of England, Wales, and Ireland, reporting 
other matters of interest connected with the same, and taking 
measures for their preservation. (Drawn wp by Dr. CROSSKEY, 
Secretary. ) 
Dorine the past year an important step has been taken towards the com- 
pletion of the researches of the Committee in one district and the giving 
a scientific arrangement to the vast number of facts that have been 
collected. 
Mr. Frederick W. Martin, F.G.8. (of Birmingham), who has made 
several valuable contributions to the reports of the Committee, has com- 
pleted the main portion of his personal survey of the boulders of the 
Midland district, and has collected together in their proper order the 
whole of the facts he has ascertained, and described with precision and 
accuracy the general results of his observations. Mr. Martin has, more- 
over, finished a map showing the distribution of the Midland boulders, 
which both corrects many errors into which previous observers have 
fallen and places the whole series of facts before the eye in a systematic 
form. The Birmingham Philosophical Society has materially aided the 
work of this Committee by including in its ‘Proceedings’ for the current 
year Mr. Martin’s notes and map. Were the same scientific method of 
treatment applied to the study of the erratics of each district in England 
and Wales results of equal value would, without doubt, be obtained. 
The Committee would strongly urge upon all local scientific societies 
to undertake this work. Not only is it of the largest value to all students 
on glacial geology, but the destruction of erratics is going on so rapidly 
that each year’s delay reduces the number of ascertainable facts. 
Without entering into the theoretical questions which are beyond its 
province, the Committee thinks it well to point out a few of the general 
results of the survey of the Midlands, in order that other observers may 
examine how far they differ from or agree with the phenomena presented 
in their respective districts. 
So far as the Midlands are concerned, the facts with respect to the 
erratics appear to establish the following points :— 
1. The boulders have been deposited at distinct periods. At least two 
of these periods can be well ascertained. In some cases the collection of 
erratics which have been supposed to show the ‘ intercrossing’ of their 
streams are really the remains of distinct periods of action ; not that there 
has been no intercrossing, but that all the supposed cases of it are not 
accurately described by that term. 
2. There are deposits of boulders in the Midland area which are 
entirely distinct from each other, boulders from special districts being - 
grouped together. 
3. There are deposits of boulders in which those from different and 
