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XX. — On the Causes of the Efficacy of Burnt Clay. By Dr. 

 Augustus Voelcker, Professor of Chemistry in the Royal 

 Agricultural College, Cirencester. 



It has been, and still is, the fate of more than one good practice in 

 agriculture to be rejected and condemned by some parties, whilst 

 others uphold and most forcibly and confidently recommend the 

 very same practice. In most instances in which we see advo- 

 cates, equally warm and eager, defending or rejecting a disputed 

 practice, we are generally safe in looking for some good which will 

 ultimately be elicited from an earnest argument of the question, 

 and we should be unwise to pass it unnoticed because we find 

 practical men disagreeing in their opinion. A careful weighing 

 of the question further will often show us that differences of 

 opinion arise frequently from the disregard or non-understanding 

 ot the primary conditions under which beneficial or contrary 

 results have been obtained. It requires but little consideration 

 to understand why one kind of manure does not exhibit the same 

 beneficial effects when applied to different crops, or when used 

 on stiff, heavy, clay land, or a light sandy, or a calcareous soil. 

 The nature of the crops, the condition of the soils, and the 

 composition of the manuring substances with which the soil has 

 been dressed, being known in these instances, we can trace the 

 beneficial action of the latter with some amount of confidence at 

 least to its cause, and are often enabled likewise to reconcile any 

 apparent contradictions which present themselves in the applica- 

 tion of manures. 



Unfortunately, however, such cases are rare ; we know, indeed, 

 little of the rationale of many processes daily practised by the 

 farmer, and we cannot feel surprised, therefore, to find the most 

 opposite opinions promulgated by different persons. A wide 

 field of inquiry here opens itself to the agricultural chemist. 

 There are many practices which are followed by undoubtedly 

 beneficial results in one part of the country, although they are 

 contrary to the usages of other localities, or opposed to the ruling 

 theories of the day ; and I am convinced the scientific investiga- 

 tion of such practices and the scrutinizing inquiry into the valuable 

 floating knowledge of many farmers will be followed by greater 

 practical results, and advance scientific agriculture more rapidly 

 than many ingenious theories have done as yet. The practical 

 man often instinctively proceeds on truly scientific principles, and 

 I am sure chemists, instead of denouncing a practice at once 

 because contrary to their favourite theory, would act much 

 wiser by endeavouring to reconcile sound practice with science. 



