192 REPORT— 1873. 



Finally, it was proposed to represent, on a duplicate map, the number, of 

 boulders and character of the rocks by disks of colour, so that a graphic re- 

 presentation of the boulders, as to position, numbers, and kind of rock, would 

 be given, and the source of any class of boulders (as granite e. g.) could be 

 readily traced. It was further proposed to number a rough rehef-map of the 

 district, so as to judge in what way the configuration of the country had 

 affected the distribution of the boulders. 



" Considerable information has been already obtained, of which the follow- 

 ing is a summary : — ■ 



•' A difficulty was experienced in defining the term boulder ; and, after 

 much discussion, it was thought that for the district the following definition 

 would serve : — ' A boulder is a mass of rock which has been transported by 

 natural agencies from its native bed.' Respecting the size at which a rock 

 may be called a boulder, it is thought better not to assign any very definite 

 limit. Some specimens, measuiing not more than a foot in some one direc- 

 tion, are both transported from great distances and glaciated, and fairly fall 

 into the categorj' of boulders. 



" Distribution of the Boulders. — The district has not as yet been sufficiently 

 examined to report fully on this question. There are unquestionably some 

 places where great accumulations have taken place, separated by country 

 with only a few boulders per square mile. The places where large accumu- 

 lations (a thousand or so) occur, as far as has yet been ascertained, are : — 



1. Tettenhall. 2. Bushbury. 3. Cannock. 



Places where moderate accumulations (50 to 100 or 200 per square mile) 

 occur : — 



Penkridge. 

 Shareshill. 

 Brewood. 

 Codsall. 



Stone. 



ShifnaU. 



Harborne, near Birmingham. 



Bridgenorth. 



" The southernmost point where boulders have been observed is on the left 

 of the lane leading from Bromsgrove Station to the town, the most eastern 

 at Bugeley, where only two or three occur. 



" It has been suggested that the cause of accumulations of boulders is due 

 to the stranding of an iceberg at the place in question ; but at present there 

 is not sufficient evidence to form any satisfactory opinion as to the cause of 

 the accumulation. 



" The boulders of the Midland district seem originally to have been im- 

 bedded either in clay or drift-sand ; but it is quite the exception to find them 

 in situ. They seem commonly to be disturbed bj- farmers in the district, who 

 meet with them when ploughing. If the boulder be of manageable size, it 

 is at once dug up and turned into the nearest ditch, or sometimes is buried, 

 or, it may be, carried to the road-side, and broken up for road-purposes. 

 Farmers find some of the boulders useful as horse-blocks, or for protecting 

 gate-posts or the corners of v/aUs and buildings ; and it is thus that many 

 are preserved. If the boulder be a very large one, it is generally left in the 

 ground, and the plough carried on each side of it. Since a plough may pass 

 over a boulder several times before the men will take the trouble to remove 

 the obstruction, there is eveiy chance for the boulder to become marked by 

 striations ; and hence much care is required in forming a judgment as to the 

 origin of striae which may be found upon it. It should be mentioned here 

 that boulders gradually 'work up' to the surface. This is due no doubt to 



