in the Island of Malta. 133 



even more distinctly than before. The same fact is ob- 

 servable in the ribbon-structure and dirt-bands of glaciers. 



3. The third peculiarity which I would mention is the 

 effect of obstruction very distinctly manifested in the same 

 stream, No. 3. 



The liquid mud appears to have pressed against the old 

 and comparatively dry mud (c), and to have been thus forced 

 to change its direction, and curve round to the right as shewn 

 in the drawing. The part of this curve furthest removed 

 from the pressure (a) still retains its concentric bands, while 

 the nearer portion (6) is altered in character ; and the cracks 

 or crevasses (which are here very numerous), assume a direc- 

 tion more in accordance with the course of the stream. The 

 old mud (C), over which the new stream does not extend, has 

 been forced by the pressure into wave-like ridges ; and that 

 when it was not in so liquid a condition as the new stream, 

 — a fact evinced by the different character of its surface. I 

 may remark, that the waves or ridges last referred to are 

 very diflPerent from those occurring in the second mud-slide. 



4. The cracks or crevasses are a fourth peculiarity ; but 

 of these I can say little more, than that they correspond, as 

 far as they go, with those which traverse the glaciers. Re- 

 marks which T have already made, and an examination of the 

 drawing, will shew that on steep inclines, and under the 

 effect of pressure, corresponding analogies are also apparent ; 

 as well as at the extremities of the streams in the mud-slide 

 and glacier. 



5. It may be permitted, in the fifth and last place, to draw 

 attention to the different states of fluidity observable in the 

 different parts of the mud-slide ; and the difference of motion 

 resulting therefrom. It seemed to me very probable that at 

 first the upper part of the mud, even some time after motion 

 has commenced, is in a more saturated state than the lower 

 parts (I know that this was the case in one instance) ; and 

 that it tends in consequence to flow down over its own in- 

 ferior layers ; so that the lower parts move more slowly, not 

 only on account of their friction along the ground, but also 

 from their inferior state of fluidity. It is possible, that this 

 may be instrumental in the formation of the concentric bands ; 



