Miscellanies. 395 
The non-fertility of bog-earths may, it appears to me, be perhaps ac- 
counted for from the organic acid they have been found to contain; sup- 
posed to be the suberic acid, but probably an acid peculiar to these earths. 
The action of the manures usually employed to bring them into a state of 
fertility, viz. lime and strong oil of vitriol, is made apparent if we take 
this view, for by uniting with the first the organic acid would be rendered 
innoxious, whilst the second would destroy it; but neither of these agents 
would have any influence on the further oxydation of the iron, and the 
second would render it soluble; and what makes this idea more probable 
is, that I have found in all rich soils a soluble organic salt of lime to exist, 
and that these soils never possessed any acid properties. ‘The poisonous 
character of the drainage water from these earths is explained by this 
view; but, on the other supposition, that it results from the action of pro- 
toxyd of iron, we can hardly imagine,—knowing as we do how immedi- 
ately, when held in solution by carbonic acid, it is decomposed by ex- 
posure to the action of the atmosphere,—that these injurious effects could 
take place in the short time that would elapse before it became sesqui- 
oxyd; and I have before pointed out that the soluble organic matter would 
have no effect in arresting this decomposition. The use of the red oxyd 
of iron in a soil has been stated to be its power of retaining ammonia. I 
must confess, however, I am rather inclined to doubt that it is of any 
great value to it, on account of this property, as all soils containing much 
of it are found to be of poor quality; but, admitting this to be the fact, 
there does not appear to me to be any reason to doubt that this retentive 
power is equallv possessed by the protoxyd. 
From the above observations I was led to the conclusion, that the pre- 
servative action of the humus on the protoxyd of iron in soils was proba- 
bly analogous to that of sugar in some pharmaceutical preparations, par- 
ticularly in that of the saccharated carbonate of iron of the Edinburgh 
Pharmacopeia. I therefore prepared some of it by the process there 
given, and found, on passing a current of air over a portion of it by the 
apparatus I have before described, that a small amount of carbonic acid 
was given out from it. J do not, however, wish to be considered as speak- 
ing positively as to this being the action of the sugar, although the experi- 
ment shown above would appear to render it probable. 
Note.—Since writing the above communication, I have had brought 
before my attention a remark occurring in several agricultural works, that 
some clays require either burning or long exposure to the atmosphere be- 
_ fore they are fitted to be mixed with fertile soils ; and as the iron in them 
is found to become peroxyd during these operations, it has been brought 
forward as another proof of the injurious action of the protoxyd of iron. 
In my opinion, however, it is not because the iron is in the state of pro- 
toxyd that clays require this treatment, but on account of its existing as 
sulphuret, which, as is well known, is hurtful to vegetation; and I believe 
