169 
THE COMPOSITION OF PEAT, AND ECOLOGICAL 
METHODS. 
J. W. HAIGH JOHNSON, B.Sc., F.L.S. 
Walton, Wakefield. 
SOME time ago, in the pages of The Naturalist, was an abstract 
from a paper read before the Botanical Section of the British 
Association meeting at Portsmouth.* This paper dealt with 
the relationship between our Moorland Flora and the com- 
position of the peaty soil supporting it. Such peaty deposits 
naturally contain a large and variable amount of water, and 
therefore on drying leave a small amount of residue. This fact 
evidently impressed the contributor very greatly as is shown 
by the unusual method of stating the results obtained. 
As a rule 100 per cent. is approximately the limit to the 
sum of the component parts of most terrestrial substances of 
which we have hitherto any cognisance. Occasionally, how- 
ever, in extremely carefully conducted analyses it has happened 
that this sum total has exceeded the usual roo per cent., 
and in one case at least, the discrepancy led to the discovery of 
an entirely new element ; but, even this error amounted to 
only three or four per cent. The author was, perhaps, led to 
emulate this classical result, and, nothing daunting, produced 
figures showing undoubtedly 170 per cent. of water, followed 
later by the incomprehensible figures of 200, 300 and even 600 
per cent. of this_substance, but these figures on closer examina- 
tion appear to be ratios and have nothing whatever to do with 
percentage composition-amounts. The misleading nature of 
these results is readily seen by comparing two peats containing 
say, 200 and 300 per. cent. of water. This, as ordinarily 
expressed, amounts to 66:66 and 75.00 per cent. of water 
respectively, so that the difference of 100 per cent. as given 
amounts to 75:00—66-66=8-34 per cent. as usually understood. 
This simple example serves to illustrate the erroneous results 
obtained by confounding ratios with percentage composition. 
It is obvious such ratios can never form a basis for comparison 
with these figures ; and to this error much of the enigmatical 
character of the whole paper may be attributed. 
In the papers quoted there is also a further difficulty namely 
that air-dry peat—which forms the basis of his figures—itself 
contains a very variable amount of water (15-25 per cent.), 
and this amount is not given in the results. The amount of 
* Report of Brit. Assoc., 1911. ‘ The Water-Content of Acidic Peats,’ 
by W. B. Crump, M.A., pp. 581 582; The Naturalist, 1911, pp. 361-362. 
‘The Wilting of Moorland Plants,’ pp. 582-583; The Naturalist, 1911, pp. 
343-344. 
1913 “April. r 
M 
