686 General Notices. 



Magazine ; especially as it relates to an article so indispensable to the garden 

 and of the nature of which so little is generally known. 



" On examining with the microscope one of the slices of coal in which Mr. 

 Witham lately discovered a distinct vegetable texture, the attention of the 

 author was excited by the remarkable appearance of several cells in that part 

 of the coal where the texture of the original plant could not be distinguished. 

 Tempted to extend the enquiry, he procured an extensive series of slices, 

 taken from the several varieties of coal found at Newcastle, and the conti- 

 guous district. The coal of the Newcastle district is considered by the au- 

 thor to be of three kinds. The first, which is the greatest in quantity, and 

 the best in quality, is the rich caking coal so generally esteemed ; the second 

 is the cannel, or Parrot coal (splent coal of the miners) ; and the third, 

 the slate coal of Jameson, consists of the two former arranged in thin 

 alternate layers, and has, consequently, a slaty structure. In the varieties of 

 coal, even in samples taken indiscriminately, more or less of the vegetable 

 texture may always be discovered; thus affording the fullest evidence, if any 

 such proof were wanting, of the vegetable origin of coal. Each of these 

 three kinds of coal, besides the fine distinct reticulations of the original 

 vegetable texture, exhibits other cells, which are filled with a light wine- 

 yellow-coloured matter, apparently of a bituminous nature, and which is so 

 volatile as to be entirely expelled by heat before any change is effected in 

 the other constituents of the coal. The number and appearance of cells 

 vary with each variety of coal. In caking coal, the cells are comparatively 

 few, and those which do exist are highly elongated. Their original form the 

 author believes to have been circular ; and he attributes their present form 

 to the distention of gas confined in a somewhat yielding material, subject 

 to perpendicular pressure. In the finest portions of this coal, where the 

 crystalline structure, as indicated by the rhomboidal form of its fragments, 

 is most developed, the cells are completely obliterated. In such parts the 

 texture is uniform and compact : the crystalline arrangement indicates 

 a more perfect union of the constituents, and a more entire destruction of 

 the original texture of* the plant. The slate coal, or the third variety above 

 mentioned, contains two kmds of cells, both of which are filled with yellow 

 bituminous matter. One kind is that already noticed in caking coal; while 

 the other kind of cells constitutes groups of smaller cells of an elongated 

 circular figure. In those varieties which go under the name of cannel, Par- 

 rot, or splent coal, the crystalline structure, so conspicuous in fine caking 

 coal, is wholly wanting ; the first kind of cells are rarely seen ; and the whole 

 surface displays an almost uniform series of the second class of cells, filled 

 with bituminous matter, and separated from each other by their fibrous 

 divisions." 



In speculating on the origin of cells in cannel coal, the author " considers 

 it highly probable that they are derived from the reticular texture of the 

 parent plant, rounded and confused by the enormous pressure to which the 

 vegetable matter has been subjected." The author next states that, " though 

 the crystalline and uncrystalline, or, in other terms, perfectly and imper- 

 fectly developed, varieties of coal generally occur in distinct strata, yet it is 

 easy to find specimens which, in the compass of a single square inch, contain 

 both varieties. From this fact, as also from the exact similarity of position 

 which they occupy in the mine, the differences in different varieties of coal 

 are ascribed to original difference in the plants from which they were 

 derived." 



Might not the volatile bituminous matter contained in the cells, which is 

 said to be " entirely expelled by heat before any change is effected in the 

 constituents of the coal," and which, consequently, carries off heat, instead 

 supplying it, be ignited, and thereby made to produce heat, by means of 

 of Witty's patent furnace. If this could be accomplished, it is probable 

 that the cannel and slate coal, which appear to contain as much of this bitu- 

 minous matter as the best, or caking, coal, might be equally available for gar- 



