Mr Witham's Observations on Fossil Vegetables. 187 



coal-fields, and lias deposits, is brown, of various tints, more 

 commonly wood-brown, frequently umber, and sometimes grey- 

 ish or blackish-brown. These fossils are all more or less cal- 

 careous, and the veins by which they are frequently intersect- 

 ed, are generally of calcareous spar. Those fossils, on the con- 

 trary, which, occurring in the same formations, are destitute 

 of organic texture, have their interior filled with substancesana- 

 logousto those of which the strata conlainingthemarecomposed. 



" Silicified fossils occur more abundantly in the superior for- 

 mations, and are generally of a lighter colour. The calcedonic 

 monocotyledonous and dicotyledonous fossils of the West In- 

 dies vary in colour from yellowish-white to reddish-brown, or 

 even bright red, but seldom or never assume tints so dark as 

 those of our inferior deposits. 



" With respect to trie fossil vegetables of which I have pre- 

 sented figures, I may here again remark, that, notwithstanding 

 the want of well-defined concentric layers in those of the coal- 

 formation and mountain limestone group, no doubt remains 

 with me as to their being Conifera?. Should it be shown, by 

 future investigations, that recent plants of other classes pre- 

 sent a similarity of structure, the case will become different ; 

 but until then, it will remain established that these fossil plants 

 come nearer to the structure of the Coniferse than to that of 

 any other tribe. As to the fossils of the lias, I presume no 

 doubt can henceforth remain in the mind of any on-e who may 

 compare them with recent Coniferas, or be satisfied with the ac- 

 curacy of my representations." 



Mr Witham concludes his highly interesting work by giv- 

 ing details of the mode in which he- prepares objects for the 

 microscope, for the process of which he acknowledges being 

 indebted to Mr Nicol. 



" Let a thin slice be cut off from the fossil wood, in a di- 

 rection perpendicular to the length of its fibres. The slice 

 thus obtained must be ground perfectly fiat, and then polished. 

 The polished surface is to be cemented to a piece of plate or 

 mirror glass, a little larger than itself, and this may be done 

 by means of Canada balsam. A thin layer of that substance 

 must be applied to the polished surface of the slice, and also 

 to one side of the glass. The slice and the glass are now to 

 be laid on any thin plate of metal, as a common fire-shovel, 



