57 



in different specimens, but is uniform throughout in the 

 case of each individual specimen. Mr. W. T. Chapman kindly 

 undertook to make an analysis of one of these, with the 

 following results : — 



Per cent. 

 Sulphur tri-oxide ... ... ... ... 32'67 



Barium oxide 



Calcium oxide 



Strontium oxide 



Alumina 



Ferric oxide 



Magnesia 



Silica 



Water 



6042 

 010 

 006 

 2-78 

 034 

 0-08 

 324 

 071 



100-40 



It will be noted that the two analyses are closely similar ; 

 the most marked differences are in the slightly higher pro- 

 portions of silica and alumina in the second instance, probably 

 arising from a small amount of clay being incorporated with 

 the barium sulphate in the nodules. They are non-crystalline 

 and amorphous in texture. 



These singular nodules are undoubtedly casts, and have 

 taken their shape from the cavities in which they were formed. 

 Their resemblance to coiled earthworms is very striking, and 

 suggests their probable origin. When holes are dug in garden 

 ground during a period of drought it is not unusual to find 

 at a considerable depth earthworms coiled up within a little 

 chamber in the dry earth. This chamber corresponds to the 

 hibernaculum, or shelter, into which hibernating animals 

 retreat during the winter, but in the case of the earthworm 

 the deep-seated cavity gives protection, not from the frosts 

 of winter, but from the heat and prolonged dryness of an 

 Australian drought. Among the nodules collected by me 

 were some that appear to be of an intermediate form between 

 the annelid-like knob and the bun-like disks. Both kinds 

 may have formed in cavities formerly occupied by annelids, 

 the difference being that in some cases the cavity has preserved 

 the true outline of the former occupant, while in others it 

 has not. 



The source from whence the barytes has been derived 

 cannot at present be definitely determined. Barium salts are 

 not infrequently found in saline waters, and the sulphates of 

 barium and lime are often found in association, as occurs in 

 the regions from which our specimens have been collected. In 

 the case of the nodules, the baryta would probably form, in 

 the first instance, a soluble bicarbonate, and then by a chemical 

 reaction with some soluble sulphate be converted into barium 



