10 



the most common being that of an elongated inverted cone, like those 

 met with in limestone caverns ; many, however, presented the appear- 

 ance and colour of white coral trees, and some, being composed of hydro- 

 carbonate of zinc, were of the dazzling white colour peculiar to that 

 mineral. 



The floor was composed of one immense bed of white hydrocarbonate 

 of zinc, of variable thickness, but in some places it was found to attain 

 a thickness of 1™ 5, — the irregularity of the ground producing a cor- 

 responding irregularity in the surface of the bed. Traces of a stream 

 were recognised, which during the rainy season traverses the cavern, and 

 which, no doubt, contributed to the deposition of the hydrocarbonate of 

 zinc. The floor was so white, that the visitors hesitated to tread 

 upon it with their muddy boots. Here and there the floor was covered 

 with the mineral in a granular form, and portions of it upon which 

 water was continually falling felt soapy. The phenomena presented 

 where the dropping occurs are very interesting, and difi'er materi- 

 ally from what are observed during the ordinary formation of stalag- 

 mites. The running water accumulated during a period of rain had 

 apparently deposited gradually a thin layer of hydrocarbonate, the soft 

 surface of which became exposed to the action of the water dropping 

 from above, as soon as the supernatant water had drained away. The 

 immediate consequence of the fall of the first drops was the formation 

 of a cup-shaped cavity. The dropping water contained some silicate in 

 solution, which immediately produced a gelatinous compound with the 

 zinc of the floor. The splash of the drop upon the soft gelatinous matter 

 threw small globules of it about. Similar little globules of soft hydro- 

 carbonate, free from silica, appear to have also been formed in the same 

 way. As the cup enlarged, several of these globules became enlarged by 

 the gradual deposition of successive layers, and, remaining in the cup, got 

 moved about, and had their surfaces polished whenever a rapid succes- 

 sion of drops fell. A rapid succession of drops, not accurately falling 

 upon the same spot, seems to have detached fragments of the more or 

 less soft mass, or floods of water may have carried broken fragments of the 

 mineral into the cups ; and being too large to be ground into round frag- 

 ments, they wore into flat lenticular or irregular pebbles. The cups thus 

 formed were filled up by the successive deposits of mineral matter which 

 floods brought into the cavern. But while on the level floor the hydro- 

 carbonate was deposited in successive laminae, the cups became the 

 moulds of concretions. In this way, probably : the cup got filled up with 

 soft mineral ; as the water drained oif, drops began again to fall into the 

 centre of the soft mass, by which a fresh cup was produced, and this 

 again filled up, and so on ; the final result being the production of a 

 kind of flattened spheroidal concretion, with a slight indentation in the 

 top. Sometimes the points from which the drops fell appear to have 

 changed,^so that no new cup was formed. In this case, the last deposited 

 matter contracted on drying, and left a slight depression, with irregular 

 lips, not unlike an opening bud. The change in the point from which 

 the drops fell was often very slight, so that a new cup was formed close 



