Miss C. A. Kaisin. On certain Structures formed 



The meshes in the network may be occupied by a finer deposit 

 arranged in successive curves. Within a coarser maze, the curves 

 are closer, and the finer material forms a more conspicuous pattern. 



In other examples, the thick streaks become less bent (cf. fig. 4 ; 

 also fig. 2), and finally straight, sometimes with a terminal knob, 

 sometimes forked or branched, generally at a rather acute angle. 

 From these axes, finer pattern-marks seem to diverge on either 

 side. Certain materials usually formed straight axes* these were 

 also developed in other substances under certain conditions, e.g., 

 when the mud was thin, or when its boundary was within the edge 

 of the cover glass, or when a corner of the cover was upraised to 

 allow quicker escape of the moisture. Thus the straight axes seem 

 to be the result of a more ready retreat of the rim generally due to 

 a freer evaporation. While, if the cover was sealed down with 

 canada balsam, or if denser mud had spread beyond the edge and 

 caked, so as to check evaporation,f a maze was produced. 



A fine pattern may be formed either in connection with the thicker 

 aggregates, or where these are wanting. It generally arises from a 

 sorting of the material the finer feathers and tufts are built of small 

 grains, the thick coarse axes of larger. The fine particles may be 

 spread almost continuously (e.g., ivory black, light red), the deposit 

 then becoming more concentrated towards a series of curving lines. 

 Similar wave patterns may become fan-like from development of 

 crossing radial curvesj (fig. 3). 



Transverse bars, also curved, extend between straight axes, where 

 these are near together, and where the fine material is abundant in 

 somewhat granular substances (fig. 2). The predominance of 

 radial or of concentric or wave pattern is mainly due to the form of 

 the area and mode of retreat, since they are shown in the same 

 material. Feather forms are developed within confined areas, as in 

 ovoid bubbles which are contained in the margin of a deposit of van- 

 dyke brown (fig. 4). 



This example (fig. 4) also illustrates other forms. The mud dried, 

 or partially dried, along part of the edge and water from the 

 included mass then tried to escape. Thus, bubbles were formed, 

 generally elliptical or ovoid, and elongated transversely to the 



* Gamboge, Upper Headon marl, boulder clay, pipe-clay, some slides of chalk, 

 a tendency in vandyke brown, sepia, vermilion, &c. 



f This was shown in one slide of vandyke brown. In another slide of that 

 material the cover was not sealed, and although the mud caked at part of the edge 

 (the part figured in fig. 4), the water escaped along most of the sides, and straight 

 axes were produced. 



j Vandyke brown, Prussian blue, crimson lake, ultramarine, vermilion, sepia, 

 chalk. 



Like chalk, pipe -clay, c; not smooth uniform substances, as vandyke brown, 

 gamboge, &c. 



