E. T. Newton— On " Tasmanite" and " White Coal." 339 



A portion of the discs carefully separated by sifting and again 

 treated with, hydrofluoric acid gave 



Combustible material 96 - 63 



Asb (brigbt red) 3'37 



100-00 

 In order to ascertain the true nature of the discs, in either Tasman- 

 ite or White Coal, it is necessary to prepare thin slices of the schist for 

 microscopic examination, and also, for the same purpose, to separate 

 the discs by treatment with hydrochloric or nitric acid. 



When the separated discs are viewed by reflected light, they 

 appear as more or less circular bodies, somewhat thickened towards 

 the circumference, many of them having their surfaces raised into 

 irregular folds. If mounted in Canada Balsam, and viewed by 

 transmitted light, many have the appearance represented in PL X. 

 Figs. 2, 3, 8, while others exhibit the folds to which allusion has just 

 been made. The more perfect discs are seen to be surrounded by a 

 double contour-line — the optical expression of the fact that these 

 discs are really thick-walled sacs. The saccular character, however, 

 is best seen in transverse sections (Figs. 1, 4, 5), or when the sac is 

 broken (Fig. 8). A closer examination enables one to see that 

 the walls of these sacs are not homogeneous. A view such as Fig. 8 

 shows numerous dots scattered over the surface, which become some- 

 what elongated towards the edges of the disc. When examined with 

 a power of about 250 diameters, the dots can be resolved into minute 

 circles about -g-oVg- of an inch in diameter with a still smaller dot in 

 the centre, as shown in Fig. 9. These structures are best seen in the 

 discs of White Coal. It may be thought that these dots are com- 

 parable to the granules to be seen upon the surface of some of the 

 macrospores of Flemingites ; but the study of transverse sections 

 shows at once that these dots are not mere surface-markings, for they 

 can be distinctly traced as minute lines (tubes ?) passing from the 

 outer to the inner surface. These lines are shown in Fig. 5, but 

 owing to the section not being quite in the same plane as the lines, 

 they do not appear to extend quite through. In addition to the 

 fine lines, the walls of the sacs exhibit obscure longitudinal markings, 

 which give them a laminated appearance (Fig. 5). 



Neither Mr. Carruthers (Geol. Mag. 1865, p. 432), nor Mr. 

 MacNaughton (Trans. Eoy. Soc. Van Dieman's Land, vol. ii. 1855, 

 p. 116), mentions any structure in the walls of these sacs. 



The discs vary in diameter, as stated by both these authors, from 

 about -Jp to 3-L- of an inch. Mr. MacNaughton speaks of a thin outer 

 coat to these discs, which may be seen when they are ruptured. I 

 have examined all my preparations, both sections and separated discs, 

 in order to distinguish this outer coat, but have been unable to do 

 so. One easily recognizes in transverse sections, such as Fig. 1, that 

 the walls of the sacs vary much as regards thickness ; and among 

 the separated sacs which are mounted in Balsam some may be seen 

 much more transparent than the rest ; but I have failed to see any 

 real difference between the thicker and the thinner sacs, or to find 

 them in anything like the relation of an inner and outer coat. 



