230 MR. J. T. CUNNINGHAM ON 



vertically into the interior (text-fig. 2). These lines and areas 

 have no relation whatever to the concentric lines or markings 

 which resemble those of molluscan shells, these markings con- 

 sisting of ridges and depressions on the surface, while the others 

 are microscopic and in the substance of the wax. 



In a vertical section from the central part of the block cooled 

 slowly in a metal mould, the stellate arrangement of the crystals 

 is visible near the free surface, and a portion of the surface shows 

 the same structure. When a superficial section of one of the 

 lateral surfaces, or the base is examined no such structure can 

 be seen, in fact crystals cannot be made out distinctly at all, the 

 whole appearance is granular and compact. 



Text-figure 2. 



J ~,\ > ^ \~\*' S 



< ' -ok a / 



n ;n\ a 



Diagram of appearance under microscope of portion of the lower surface of a 

 shell-like plate of paraffin-wax, cooled by contact with water. 



My conclusions from these observations is that the large 

 prismatic crystals are formed where the cooling is slow and that 

 they assume the stellate arrangement where there is most freedom 

 of movement, i. e. near or at the free surface, as on a glass slide 

 or at the surface of a block, or floating shell-like mass. On the 

 other hand, where the cooling is rapid, as at the surface in contact 

 with water or in contact with the metal of the mould, neither 

 large crystals nor stellate arrangement is to be seen, the structure 

 is more compact, apparently because the wax becomes solid at 

 numerous closely crowded points at the same time, and crystals 

 if formed at all are very minute. I have not been able to see any 

 indications of crystals having any approximation to a spherical 

 form, which I presume is the meaning of sphsero-crystals. I am 



