174 DR BENNETT ON THE STRUCTURE OF THE 



now went over the sections of coal in the rich collection of Mr Alexander Bry- 

 son of this city, and subsequently carefully examined the numerous sections made 

 by Dr Adams of Glasgow. Before the trial of Gillespie versus Russel came on, 

 Dr Adams, Mr Quekett, and myself, spent nearly an entire day together, exa- 

 mining each other's specimens, and carefully re-investigating the whole subject. 

 It was then that the character of the ashes in the various substances we had 

 examined was pointed out to me by Dr Adams, who, in my opinion, is entitled 

 to the greatest credit for the laborious, skilful, and successful efforts he has made 

 in determining the structure of numerous coals, and pointing out the differences 

 they exhibited, when compared with the Torbanehill mineral. At this meeting, 

 also, we compared the structure of coal with various kinds of recent woods, we 

 incinerated the mineral and certain coals, and carefully examined the ashes ; 

 and there was established, as the result of this conjoined investigation, as well as 

 from the independent researches made by Dr Adams in Glasgow, by Mr Quekett 

 in London, and by myself in Edinburgh, the most perfect accord with regard to 

 all the facts which had been elicited during the inquiry. 



At the commencement of the present session, I brought the subject under the no- 

 tice of the Physiological Society of this city, who appointed a committee, composed 

 of four gentlemen in addition to myself, all of whom had long been accustomed 

 to the use of the microscope, and were familiar with vegetable and animal struc- 

 tures. Three of these gentlemen, viz., Dr Cobbold, and Messrs Barlow and Kirk, 

 made farther inquiries and researches, which served to elicit additional facts, 

 and to demonstrate, in the language of their report, that " the Torbanehill mi- 

 neral is widely different from every kind of coal."' Lastly, with a view of meet- 

 ing certain theoretical objections which have been advanced, I have carefully 

 examined the structure of various kinds of peat, as well as the stems of recent 

 ferns and several fossil plants, which have only served to establish the entire ab- 

 sence of connection between these substances and the Torbanehill mineral. 



In now endeavouring to place in a condensed form the results of this extended 

 investigation before the Society, I propose, in the first place, to describe the facts, 

 as they may be easily demonstrated in the field of the microscope : Secondly, to 

 deduce from these facts the structural element which distinguishes every kind 

 of coal from the Torbanehill mineral, and explain the cause of the differences 

 which are recorded in the proceedings of the recent trial : Lastly, to offer a few 

 speculations as to the nature of this mineral, as distinguished from various kinds 

 of household and cannel coals. 



I. When we examine a piece of undoubted coal, such as of the Zetland or Buc- 

 cleuch coals, it presents to the naked eye a fibrous structure, and has a black 

 shining streak. It has been found difficult to make thin sections of it, as in the 

 grinding process it readily crumbles down. But when a tolerably thin slice, made 



