150 Mr Nicol on the Structure of 



which they were taken, have expressed the same opinion of their 

 general accuracy. 



Having thus given a brief description of the structure of se- 

 veral individuals of the family of recent Coniferae, I shall now 

 subjoin a few observations on the structure of those which occur 

 in the earth in a fossil state. Some of the fossil Coniferoe have 

 distinct annual layers, others have none. The first kind more fre- 

 quently occur than the second, but the second have been met with 

 in various places. In the lias formation in the vicinity of Whitby, 

 I found a small specimen, which, although it displayed the coni- 

 ferous texture in a very perfect state, showed no indication of 

 distinct annual layers. This specimen was entirely siliceous. 

 Similar masses of considerable magnitude, also siliceous, have been 

 found in the Newcastle coal-formation ; and in the sandstone 

 quarry of Craigleith, several trunks of large dimensions, first 

 pointed out to naturalists by Professor Jameson, have been found, 

 without any appearance of annual layers *. These, however, are 

 chiefly composed of carbonate of lime, blended with a portion 

 of iron and carbonaceous matter. The trunk which was dis- 

 covered in that quarry in October last (1833), is perhaps the 

 most magnificent specimen of a coniferous petrifaction that has 

 ever been seen. It is nearly round, and nearly three feet in 

 diameter. In its position it declines from the vertical about 

 33°. Fourteen feet of it have already been laid bare, and 

 every precaution is taken to preserve it entire until it be wholly 

 dug out. When that happens, it will probably soon after be 

 deposited in some one of the scientific institutions of Edinburgh. 

 When this trunk was first observed, some fragments were de- 

 tached from its upper extremity. From the most solid of these 

 I have cut several sections, both transverse and longitudinal, 

 with a view to examine its structure. One of these specimens 

 measures about twenty square inches. Throughout the greatest 

 part of its surface, the coniferous texture exists in a very per- 

 fect state of preservation, but towards one of its extremities the 

 vessels are very much contorted, and in one small part completely 

 obliterated. 



The colour of this tree is in the transverse fracture greyish- 

 black ; in the longitudinal fracture brownish-black. Throughout 

 • The largest of these is figured in Mr Witham's work. 



