310 Intelligence arid Miscellaneous Articles.' , ' 



mate of the period, in the northern temperate zone, was of such a 

 character that the true conifers show rings of growth not larger, or 

 much less distinct than those of many of their northern congeners*. 

 The Sigilloriee and Calamites were not, as often supposed, succulent 

 plants. The former had, it is true, a very thick cellular inner bark ; 

 but their dense woody axes, their thick and nearly imperishable outer 

 bark, their scanty and rigid foliage would indicate no very rapid 

 growth. In the case of Sigillarice, the variations in the leaf-scars 

 in different parts of the trunk, the intercalation of new ridges at the 

 surface representing that of new woody wedges in the axis, the 

 transverse marks left by the successive stages of upward growth, all 

 indicate that at least several years must have been required for the 

 growth of stems of moderate size. The enormous roots of these 

 trees, and the conditions of the coal-swamps, must have exempted 

 them from the danger of being overthrown by violence. They pro- 

 bably fell, in successive generations, from natural decay ; and, mak- 

 ing every allowance for other materials, we may safely assert that 

 every foot of thickness of pure bituminous coal implies the quiet 

 growth and fall of at least fifty generations of Sigillarice, and there- 

 fore an undisturbed condition of forest-growth enduring through 

 many centuries. Further, there is evidence that an immense amount 

 of loose parenchymatous tissue, and even of wood, perished by decay; 

 and we do not know to what extent even the most durable tissues 

 may have disapjjcared in this way ; so that in many coal-seams we 

 may have only a very small part of the vegetable matter produced. 

 Lastly. The results stated in this paper refer to coal-beds of the 

 middle coal-measures. A few facts which I have observed lead me 

 to believe that in the thin seams of the lower coal-measures remains 

 of Noeggerathia and Lepidodendron are more abundant than in those 

 of the middle coal-measuresf. In the upper coal-measures similar 

 modifications may be expected. These differences have been to a 

 certain extent ascertained by Goeppert for some of the coal-beds of 

 Silesia, and by Lesquei'eux for those of Ohio ; but the subject is 

 deserving of further investigation, more especially by the means pro- 

 posed in this paper, and which I hope, should time and opportunity 

 permit, to apply to the seventy-six successive coal-beds of the 

 South Joggins. 



XLVIII. Intelligence and Miscellaneous Articles. 



STEAM-SHIP PROPULSION. 



THE following are the results of an anticipative calculation of 

 the probable speed of the ' Great Eastern ' in nautical miles an 

 hour, with different amounts of indicated horse-power, when drawing 



* Paper on Fossils from Nova Scotia, Proc. Geol. Soc. 1847. 



1 1 may refer to my late paper on Devonian Plants from Canada for an exam- 

 ple of a still older coal made up principally of remains of Lycopodiaceous plants 

 of the genus Psilophyton. 



