332 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1956 



Second, the proponents of the algal theory overlook or minimize 

 two important conditions in the geologic origin and occurrence of 

 thunder-eggs that affect adversely the interpretation of the filaments 

 as algae. All students of igneous rocks agree that spherulites of 

 the kind that become thunder-eggs are bom in a hot extrusion of sili- 

 ceous, eruptive material from a volcano or volcanic vent soon after the 

 flow comes to rest but before it becomes rigid and before prismatic 

 structures develop. This chemically complex mixture of minerals, liq- 

 uids, and gases may congeal more or less quickly into obsidian, perlite, 

 or vitreous, welded tuff. Thus the emplacement and early stages 

 of the lava require a temperature so high and sterilizing that no algae 

 or other forms of life can survive in the resulting spherulites or their 

 cavities. Moreover, the incipient thunder-eggs are buried and com- 

 pletely enclosed by surrounding matrix so that no sunlight what- 

 ever can penetrate and relieve their pitch-darkness. Hence, even if 

 it be granted that the temperature of the lava after the cavities are 

 formed becomes low enough to permit algae to enter, no algae under 

 this unfavorable light condition can be expected to survive therein, 

 for all algae require some light, much or little, as the case may be. 

 I conclude, therefore, that the physical features of the filaments and 

 the geologic conditions accompanying their origin forbid their iden- 

 tification as algae, mosses, or any other organisms. 



THE PSEUDOALGAE, CHEMICAL GARDENS 



If the filaments are not algae but inorganic structures, what is their 

 nature and genesis ? An intelligible answer to this question demands 

 first a closer inquiry into the origin of the cavity fillings in which 

 the filaments are found embedded. These parts of thunder-eggs are 

 chiefly chalcedony and in section are variously shaped, either geometri- 

 cally regular or grotesque and fantastic (pi. 1 ; pi. 2; pi. 3, fig. 1 ; pi. 6, 

 figs. 1, 4) . Much depends upon the direction of cut, and the kind of 

 figure expected can often be confidently predicted before cutting by 

 studying the ridges on the surface, for these are the outward ex- 

 pression of the internal angular projections of the "stars," "cubes,"' 

 and other forms. After all the external altered matrix is removed 

 many of these chalcedonic interiors look like cubes with hopperlike 

 cavities for sides (pi. 3, fig. 3), often with a ball at the center of one 

 side and an opposing socket at the other. The thunder-eggs con- 

 taining such figures (pi. 1, fig. 1 ; pi. 3, fig. 2) seem to show that the 

 vitreous lava when still sufficiently soft was pulled or forced apart, 

 for little effort of imagination is needed to collapse the boundaries 

 of the cavities so that the arch of the ball, for example, will receive 

 the opposite socket, and other features of the outline fit roughly into 

 place. Nevertheless, as in other complex matters, the doctors disagree 

 about the method of origin of the cavities, some claiming expansive 



