On the Structure and Formation of Coal. 157 



"Four Feet" seam wood- tissue undoubtedly contributed to it; 

 whether spores did was uncertain; it was true they could be 

 detected in it. In the second bed of the shallow seam they had a 

 very different coal from the upper one. It was made up almost as 

 a whole of hydrocarbonaceous material. Yery few spores could be 

 detected. It was possible that the scarcity of these objects might be 

 due to decomposition ; but the author's investigations seemed to show 

 that spores resisted decomposing influences more effectually than 

 wood-tissue, which seemed to account for the fact that where they 

 occur they stand out in bold relief against the other material com- 

 posing the coal. Below the central bed of the shallow seam came the 

 main division. In it the author detected a large accumulation of 

 spores, but hydrocarbon formed a fair proportion of the mass. The 

 author referred to other seams of coal from various parts of England, 

 and pointed out the structure of each bed composing them. The 

 conclusions on the evidence elicited from his investigations were (1) 

 that some coals were practically made up of spores, others were not, 

 these variations often occurring in the beds of the same seam ; (2) 

 that the so-called bituminous coals were largely made up of the sub- 

 stance which the author termed hydrocarbon, to which wood-tissue 

 undoubtedly contributed. 



An appendix to the paper, written by Prof. Harker, Professor of 

 Botany and Geology at the Royal Agricultural College, Cirencester, 

 dealt with the determination of the spores seen in Mr. Wethered's 

 microscopic sections. Taking the macrospores, the resemblance to 

 those of Isoetes could not fail to strike the botanist. He had 

 procured some herbarium specimens of Isoetes laeustris in fruit, and 

 compared the spores with those from the coal. When gently crushed, 

 the identity of the appearance presented by these forms from the 

 coal was very striking. The triradiate markings of the latter were 

 almost exactly like the flattened three radiating lines which mark 

 the upper hemisphere of the macrospores of Isoetes laeustris. The 

 writer therefore concluded that the forms in the coal were from a 

 group of plants having affinities with the modern genus Isoetes, and 

 from this Isoetoid character he suggested for them the generic title 

 of Isoetoides. pending further investigation. 



2. " On Strain in connexion with Crystallization and the Deve- 

 lopment of Perlitic Structure." By Frank Rutley, Esq., F.G.S. 



In a paper read before the Society and published in the ' Quar- 

 terly Journal' (vol. xxxvii. p. 391) some observations were made 

 upon microscopic areas of depolarization in an obsidian tuff from 

 Montana, U.S. The paper now read related to a further examina- 

 tion of similar phenomena in an obsidian from Java. The glass 

 adjacent to the numerous crystals occurring in this rock exhibits 

 depolarization, as in the case of the Montana tuff. In some instances 

 a perlitic structure surrounds the crystals, and the depolarization 

 then ends abruptly at the fissure. One instance is described in 

 which such a fissure only partially encircles a crystal, and the de- 

 polarization is then seen to end abruptly at the fissure and also to 



