1882.1 



MICEOSCOPICAL JO[JKNAL. 



211 



terrestrial surface. Layers of lime- 

 stone and coal, sometimes of immense 

 extension both in the vertical and in 

 the horizontal direction, are produced 

 for the most part by the aid of or- 

 ganisms of both animal and vegetable 

 nature, commonly of microscopic 

 size. The history of the formation of 

 these minerals, produced exclusively 

 by the aid of vegetable life, as well as 

 the question about the true nature 

 of them, has not yet come to any de- 

 finite conclusion. The formation of 

 these minerals fills up an important 

 chapter of the life-history of the 

 earth. A large amount of carbonic 

 acid, in devonian and silurian times, 

 diffused in the atmosphere, was with- 

 drawn from it under the influence 

 and by the aid of a most energetic 

 development of vegetable life; and 

 thus produced the conditions of exis- 

 tence for higher animal life. I may 

 be permitted briefly to allude to the 

 various views and experiences about 

 this mineral, so important for modern 

 life, and so remarkable both from its 

 microscopical structure and its che- 

 mical composition. The writers on 

 natural history of ancient times do 

 not make any mention of it. The 

 first writer who makes mention of 

 coal, under the name of combustible 

 fossils, is Agricola, the founder of 

 mineralogy. ***** 



The first observation of the ve- 

 getable structure to be seen in coal 

 was published in that year. The 

 first observer, Hutton, says that 

 in each of the three common sorts 

 of coal in England, anthracite, 

 slaty, and cannel coal, more or less 

 vegetable structure can be seen. 

 This observation has been confirmed 

 by Goppert, and he mentions a new 

 method of examination, by burning 

 off the coal and determining the 

 structure of the skeleton of ash which 

 is left. 



From the first observations of Hut- 

 ton and Goppert until the present 

 time the general knowledge of the 

 microscopical structure of coal has 

 been increasing. Through observa- 



tions of Bailey, Dawson, Quekett, 

 Newton, new bodies, unknown before 

 as constituents of coal, have been 

 added to the bodies of reticular struc- 

 ture previously known. The know- 

 ledge of the flora of the higher plants 

 of the carbon period has been ad- 

 vanced through the excellent works 

 of Goppert, Andrae, Weiss, and 

 Williamson, but the knowledge of the 

 microscopical structure, and of the 

 various constituents, of coal did not 

 make equal progress. The principal 

 reason of the difficulty of penetrating 

 into the darkness of the coal sub- 

 stance, and getting clear observation 

 of the microscopical structure and 

 composition was this, that it is next 

 to impossible to obtain, as can be 

 done in the case of most other mine- 

 ral substances, microscopical sections 

 of such a degree of transparency that 

 all bodies composing the substance 

 become discernible. Coal seems to 

 have opposed,, obstinate resistance to 

 all efforts; it has resisted the most 

 powerful solvent of the structure of 

 vegetable tissues, a mixture of chlo- 

 rate of potash and nitric acid. There 

 has been no doubt that the bodies 

 seen at first by Hutton arise from 

 plants; but the question was, if there 

 were in those bodies in the coal any 

 things analagous to our recent veg- 

 etable tissues, and, in case these bo- 

 dies were remains of plants, if there 

 were any identity with the cellular 

 tissue of those plants, from which the 

 coal could have originated. Obser- 

 vations on peculiar bodies of constant 

 form and more transparent nature, 

 claimed as belonging to the class of 

 spores, have been the last important 

 contributions to the knowledge of the 

 microscopical constitution of coal. 

 Dawson makes mention of numerous 

 spores inclosed in the torbanite of 

 Scotland and in the tasmanite of 

 Australia, "little disks of dirtyish 

 yellow color," and found in many 

 coals and slates, but not in so great 

 numbers. Observations have been 

 made by Newton on bodies in the 

 coal of peculiar form, and very pro- 



