Vol. 58.] CONCRETIONS IN THE LOWER COAL-MEASURES. 47 
In many cases it is easy to detach large pieces of fossil wood 
from these concretions. Several samples of this fossil wood have 
been analysed by me with the following results * :— 
16 II. III. LV. 
Per cent. Percent. Per cent. Per cent. 
IBEPPOUS GRICE! 5.5c< cic casccniocccas 0:79 3o14 0°60 1-91 
IIGERIG OXIUE 2.05 So. nec conse oo tes = 1:60 0°59 RTT) 
Js VISTA ea Sa 0-01 == = = 
PNG cc 19s 5 Se Be. 48°32 18:05 49°61 30°49 
PPR OSI A, fo cn ace sas akapeneabnn es 1-73 O71 1:52 2°96 
Sam phuUrie Acid 02. -accrcosssan aes: trace 6°70 0°60 4°32 
SALVOMIG ACIG) co.ssaee ieessstovone. notestimated 11°80 39°09 26-80 
STU EE Goneaee ite al eet ca aR Rr PLLA do. 0°30 ‘O01 ‘08 
BFan-pyrities 4226.0 15.51 Boson totes do. 48°63 4°75 24:25 
Oreamic matter . 5 h.3.0.5, 05000. do. 403. 3°48 4°79 
Water and matter volatilizing 
Sioe WN) ool Oi eels Rie. fon ee ee do. 4°25 0:25 161 
: 99:21 100-45 99-98 
The constituents of the samples of fossil wood may be calculated 
as follows :— 
i i II. III. IV. 
Per cent. Percent. Per cent. Per cent. 
Ferrous carbonate .........s0028- 1:44 . O77 1:12 3°57 
INGETIE OXING, 2250-23 co eyes. seseedss — 1:60 0°59 PRTG 
Calcium-carbonate ..............- 86°30 23°88 87:01 49°05 
Magnesium-carbonate ............ 3°63 1-49 3°19 6:21 
Calcium-sulphate .........:...« not estimated 14°40 1:29 9:28 
CELT Se Se Oe A ii a aE Be do. 0:30 0:01 0°80 
BEG PYTILCR ei. icsgecesonesrestas do. 48°63 4°75 24:25 
Rrpetviic MEMELER 15082. o2e ence: do. 4:03 3°43 4°79 
Hygroscopic water ............+6. do. 1:37 _ — 
From the foregoing analyses it is apparent that the fossil wood 
and also the concretions themselves are made up very largely of 
two constituents—calcium-carbonate and iron-pyrites; and that 
there is great variation in their relative amounts. 
Since the first analyses of these concretions were made, it has 
been my wish to arrive at some knowledge of their genesis and 
mode of formation, and seeing that very little but speculation has 
hitherto been accomplished in this department of geology, it was 
necessary to perform a large number of experiments, which happily 
led to an understanding of the conditions under which such con- 
cretions may have been produced. 
These experiments will be described in the present paper, but 
before they are detailed it will be interesting to recapitulate the 
little that geologists have had to say about concretions. 
The late E, W. Binney, who devoted much of his leisure to the 
preparation and examination of sections of ‘ coal-balls,’* stated that 
1 Proc. Roy. Soc. Edin. vol. xx (1893) p. 71. 
2 Proc, Manch. Lit. & Phil. Soc. vol. v (1865) pp. 61, 62. 
