126 



PROCEEDINGS OF SECTION B. 



of molecules may be used the equations look very pretty. One 

 can substract any acquired number of molecules of CO2 H2 O and 

 CH4 from Cg Hio Og or a multiple of it and obtain a residue 

 corresponding to anything from free carbon to cellulose itself. 

 These views are again set forth in one of the latest chemical works 

 bearing on the subject, viz. "Wanklyn's Gas Engineers' Chemical 

 Manual." In connection with this I would point out that in most 

 coals the woody fibre, which contains the greater portion of the 

 cellulose in modern plants, is represented by almost pure carbon 

 forming the so-called " mother of coal " or mineral charcoal. As 

 cellulose was so converted it is an untenable position that other 

 portions of the same substance should under the same conditions 

 be converted into bituminous matter. 



On the other hand mineralogists and geologists generally, lay 

 great stress on the conditions under which the deposit of coal was 

 formed and refer particular varieties to different horizons as a 

 reason for their difierent composition and properties. This can be 

 made to agree with the chemical hypothesis mentioned as it may 

 be said that different qviantities of tlie products would be formed 

 under varying conditions. 



There are others who acknowledge that there are at least three 

 conditions which modify the compositon of the mineral. Thus 

 Percy recognises the fact that difference in the composition of 

 vegetable matter due to resinous bodies, etc., may by increasing 

 resistance to decomposition tend to preserve vegetable structure 

 (Fuel, p. 270.) Dana says " Coals were once beds of vegetation, 

 analogous in most respects to the peat beds of modern times " 

 (Mineralogy, p. 758), and on the succeeding page, " between 

 excluded air and imperfectly excluded, and of pressure from 

 heavy superincumbent earthy beds and little or no pressure lie the 

 conditions which attended the origin of the various kinds of coal 

 and determined, in connection ivith the nature of the vegetation itself, 

 tlieir tx'ansformation in progress." From various observations the 

 writer has come to the conclusion that the words put in italics by 

 himself are of more importance than is usually assumed and that 

 this idea is probably the most important of all. This condition 

 is placed first in a sentence in Ronalds and Richardson's 

 "Knapp's Technology," (I., p. 765), where it says — "The varieties 

 of coal may depend on the nature of the plants that composed it, 

 the varied circumstances attending their deposit, or the varied 

 conditions under which the beds have subsequently been placed." 



My thoughts were first directed to the probable comparatively 

 great importance of the original composition of the plants 

 through examining a number of brown coals from New Zealand, 

 Victoria, Western Australia, and New South Wales, and which 

 I found could be divided into four classes. 



1st. — Those containing fossil resin (retinite) distributed througli 

 them in grains from the size of pin heads to that of 



