20 ON THE STRUCTURE AND MOTION OF GLACIERS 
covered all over with small circles similar to those between the points 
ab and a’b'. The mud was then permitted to flow, and the mechanical 
strains exerted on it were inferred from the distortion of the small 
circles. The figure represents the result of the experiment. The 
straight rows of circles bent in the first place into curves; at the 
point A both streams met, and by their mutual push actually squeezed 
Fig. 9. 
R S 
the circles into lines. Along this central portion in the glacier itself 
the great medial moraine stands, and under it and beside it, as already 
stated, the lamination is most strikingly developed; the blue veins 
being parallel to the axis of the glacier, or, in other words, coinciding 
with the direction of the central moraine. Midway between the 
moraine and the sides of the glacier the structure is very imperfectly 
developed ; and the deportment of our mode!, which shows that the 
circles here scarcely change their form, tells us that this is the result 
