Correspondence. 437 
unable to find a more detailed account, but the length of the abstract 
was quite sufficient to admit of a clear statement ! 
The two essential points of this abstract are :—(1) the so-called water- 
content figures and (2) the convenient method formula for obtaining the 
humus-content. ; 
(1) The term ‘water-content’ has a very definite and restricted 
meaning, 7.e., the amount of water which.a given substance contains— 
and if expressed as a percentage composition—the sum total of the con- 
stituents must amount to 100. Thus three wet peats might have the 
following compositions :— 
Water vs ‘a vite 90:0 80-0 60:0 
Humus sf re at 9°7 18-0 35°0 
Ash or Mineral 3 2:0 5:0 
100-0 100-0 100-0 
and these when dry would contain :— 
Humus ap ae ond 97°0 go-o 87°5 
Ash ae a Bi 3:0 10-0 12°5 
100-0 100:0 100-0 
Water absorbed .. be goo 400 150 
But Mr. Crump frefaces each of the second series of figures by the 
amount of water which was originally associated with the too parts of the 
now dry peat, viz., 900, 400, and 150, and does not make the slightest 
distinction between this water which the peat did contain and the true 
constitutional percentage of the dry peat. This is further complicated by 
a ‘refinement ’ whereby the standard ‘ dry’ peat is ‘ air-dry,’ and there- 
fore still contains some moisture, the amount of which is not given. It 
obviously follows that these amounts ‘ being additions to the roo parts’ 
are in no sense ‘content’ figures, but slight variants—for the reason 
given above—of the water absorbed figures under the existing humidity 
conditions at the time of sampling, and are comments upon the analyses 
which naturally they should follow. 
One would like to know what further justification there is for adopting 
a 15°C. air-dried basis in preference to the usual 100° C. basis. 
It is a well-known laboratory practice to air-dry soils for convenience 
in storing. The temperature used is generally about 15°C. because this 
temperature does not seriously affect the physical properties of the 
material, as would be the case if a higher temperature were used. 
This basis is both essential in laboratory work and useful for 
comparative purposes, but to attempt to establish it as a standard is a 
very serious matter, and such needless and useless additions should be 
severely deprecated. The mere unavailable nature for plant-life of the 
water remaining at 15° C. cannot justify adding another to the already 
too long list of standards, for obviously this is but a partial statement 
regarding the amount of unavailable water as much of that Jost at 15°C. 
is likewise unavailable. Heinrich has already shown that peat-vegetation 
wilts when the amount is from 2-3 times that of the air-dried material, 
and necessarily plants vary in their capacity for utilising such water so, 
strictly speaking on such a basis a different drying temperature should be 
adopted for each plant or plant association. 
Furthermore, the substitution of this 15°C. basis for the more general 
100°C, renders useless for comparative purposes countless thousands of 
analyses already on record, and totally annuls the advantage of the 
“water-absorbed’’ basis used by Mr. Crump because a second variable 
1913 Dec. 1. 
