596 



C. EICKETTS ON THE EKEATICS ITi THE 



greater axis somewhat removed from the perpendicular with a 

 small detached portion lying nearly at a right angle to its original 

 position, the thinner and lower part not being entirely displaced, 

 through resting on a slight projection at the lower end of the 

 fracture (fig. 3). 



Similar glaciated pebbles " split and shattered by the frost " into 

 fragments which still remain exactly in apposition are, in many 

 districts, buried in moraine accumulations formed on land. These 

 fractures must have occurred subsequently to the envelopment of 

 the blocks in glaciers, otherwise the pieces could not have con- 

 tinued so accurately in position whilst moving beneath such a burden. 



Pig. 3. — Silurian pebble split, separated, and dAsplaced, as in situ in 

 Boulder-clay, Rock Ferry. (One third natural size.) 



Some erratics are so sculptured into forms dependent on differences 

 in their texture, that the less easily disintegrated portions, and the 

 harder materials filling shrinkage -joints, stand prominently in relief ; 

 some are so fashioned and modelled that every bed, however thin, is 



Pig. 4. — WeatJiered block from 

 Boulder-clay. (One third 

 natural size.) 



Fig. 5. — Weathered block with 

 smoothed surfaces from 

 Boidder-clay. (One third 

 natural size.) 



X . Smoothed surfaces. 



conspicuous. There exists a great similarity between some such spe- 

 cimens from the Boulder-clay and others in moraine accumulations 

 (compare figs. 4-7). This is remarkably the case with two from a 



