Geological Relations of the East cf Ireland . 291 
we may in general perceive in the roof a leader of coal, one or two 
inches in thickness, and another next to the floor a few inches 
thick. These enlarge as the hag decreases, until they meet and re- 
constitute the seam. 
§ 196. The roof shale, or slate clay of the coal troughs is of 
various shades of blackish grey. Immediately above the coal it 
abounds in vegetable impressions, and it contains flat nodules of clay 
ironstone for about four feet above the coal. The impressions, 
when fresh, exhibit a glossy, silky lustre, and evidently consist of 
thin pellicles of coaly matter, which in some of the larger kinds 
possess a discernible thickness. On comparing a suite of these 
specimens with Parkinson’s Organic Remains, and with Martin’s 
Petrificata Derbiensia, and on submitting them to the examination 
of some of my botanical friends, the following analogies were con- 
ceived to be established. 
Some of the impressions resemble Martin’s PI. 13. fig. 3. (which 
occurs on the Derbyshire shale, ironstone, and sandstone) ; and Par- 
kinson’s vol. i. PI. 1. fig. 6. (which occurs on shale), and PI. 3. fig. 
4. (which occurs on sandstone.) These impressions seem referable 
to the stem of one of the Pines. 
Others resemble Martin, PL 25. fig. 1. and PI. 26. fig. 2. (which 
are both on the Derbyshire sandstone) ; and Parkinson, vol. i. PI. 
3. fig. 3. (which is on sandstone). The prototypes of these are 
considered as belonging to the equisetum ; but of much larger 
dimensions than any now known to exist. 
Some of the impressions are conceived to be referable to the 
hippuris, which seem also to bear some analogy to Parkinson, 
vol. i. PI. 5. fig. 3. (which is on shale), and fig. 7. (which is on 
ironstone), and considered by that author as belonging to one of 
the verticillatse. 
2 o 2 
