Structures formed in drying Fluid with Particles in Suspension. 217 



" On certain Structures formed in the drying of a Fluid with 

 Particles in Suspension." By CATHERINE A. RAISIN, B.Sc. 

 Communicated by Professor T. G. BONNET, D.Sc., LL.D.,. 

 F.R.S. Received March 16, Read May 5, 1898. 

 (PLATE 2.) 



PAET I. 1. Origin and Method of Experiments. 



2. Classification of Forms produced. 



3. Conditions and Causes of Formation. 



4. Possible Applications in Nature. 

 PAET II. 5. Results affected by Crystallisation. 



PART I. 

 1. Origin and Method of Experiments. 



I have frequently had to mount in water, for examination with the 

 microscope, the powder of various rocks. Certain of the slides,, 

 when accidentally dried, exhibited rather interesting forms. These 

 I showed to Professor Bonney, who encouraged me to try for farther 

 results, so the experiments were continued with various powdered 

 substances many pigments (vermilion, indigo, sepia, &c.), chalk 

 and other more or less friable rocks. At first, ordinary microscope 

 slides were used, hut afterwards, larger pieces of glass, in each case, 

 generally with a cover-glass placed over the mud. The results 

 seem to be worth describing, as affording familiar, almost homely 

 illustrations which may throw some light on the origin of certain 

 minor structures in rocks. 



2. Classification of Forms. 



The chief effects produced may be shortly described. One form- 

 shown by the dried powder is that of a winding network (Plate 2, fig. l) r 

 which is formed of bent stems, fairly uniform in thickness, giving 

 rise to short branches in different directions, but generally at high 

 angles. The whole makes a kind of maze in which the broader 

 winding spaces often average from T \ inch to ^ inch in width. 

 This form arises from desiccation of a fairly dense* mass. Where 

 it is densest, a coarser maze is developed and the coarser part is 

 earlier formedf (fig. 1 towards a and b). 



* I use this term for a mass where the water is distinctly "muddy," i.e., where 

 the proportion of the suspended particles to the water is relatively high. 



t Sometimes the denser mud has been carried forward apparently b}' the 

 squeezing along of more suspended material (fig. 1). Sometimes a greater amount 

 of the solid substance has been left behind, while a less dense mass was pressed 

 forward. In slides left to dry in a tilted position, gravitation carried the g- eater 

 amount of particles towards the lower end. 



