EECEEATIYE SCIENCE. 



347 



ture displayed in Fig. 3 is similarly, tliough 

 variously, marked in several other sections 

 in the same direction. 



A longitudinal concentric section of an 

 araucaria, from Moreton Bay, New Holland, 



Fig. 3. 



(a recent wood) is shown in Fig. 4. The 

 celebrated Craigleith tree, found fossil in the 

 sandstone quarry at that place (near Edin- 

 burgh) in October, 1833, is a very fine spe- 

 cimen of a coniferous petrifaction, and very 

 much resembles in its general characters the 



Fig 4. 



araucaria of jVIoreton Bay. In a longitutli- 

 nal section (parallel to a radius) of this tree, 

 the vessels in general are very much dis- 

 torted, and the whole texture greatly ob- 

 scured ; but when the vessels appear with 

 any distinctness, they often contain discs in 

 double, triple, and quadruple rows, though 

 the discs are always obscurely seen. The 

 general conclusion arrived at by Mr. Nicol, 



after all his examinations, is, that all ihe fossils 

 retaining the ligneous structure in the coal, 

 from these formations, are of coniferous origin. 

 Having already named cannel-coal, we 

 may explain its character. It burns as clearly 

 as a candle, when once ignited at a flame, 

 and hence its name, which is a corruption of 

 candle-coal. But it flies ofi" (decrepitates) in 

 small fragments, with a cracking noise, when 

 flat pieces are placed upon a fire. Its colour 

 is grayish black or brown, its lustre is resin- 

 ous, and it is so compact that it can be 

 worked in blocks and turned in a lathe, and 

 is susceptible of a good polish. It is, there- 

 fore, often fashioned into a variety of orna- 

 ments, and has so much the appearance of 

 jet as to deceive all but careful observers. 

 The streak is, however, very difierent from 

 that of jet. So bituminous is it, that in 

 making coke or gas it is mixed with the 

 smallest of the best coal. The collieries of 

 Wigan, in Lancashire, afford considerable 

 quantities of cannel-coal, and it is also found 

 in pits near Coventry, and at Lesmahago, 

 not far from Glasgow. Mr. Witham found 

 distinct traces of organization in ' it under 

 the microscope. From its compact nature 



Fig. 5. 

 sections of it are not difficult to form, and 

 tliey will reward the observer. Fig. 5 ex- 

 hibits a section of cannel-coal, wherein the 



