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have stated above, and the experiments tried, are sufficient 

 testimony to the correctness of the theory of those eminent 

 gentlemen, and prove that the double decomposition does 

 actually take place. Having satisfied myself that great benefit 

 might be derived from the application of gypsum, it struck 

 me that it was possible to find the same properties, though in 

 an inferior degree, in some of the unsightly masses of refuse 

 surrounding coal mines. I therefore proceeded to examine 

 the following substances, namely, common coal ashes, burnt 

 slack or refuse small coal, mixed with drosses or iron pyrites, 

 burnt blue metal or indurated clay, found in sinking pits, and 

 frequently forming the roof and floor to coal, in which are 

 often embedded fossil shells and vegetable remains, the whole 

 turning to a red colour when burnt ; and other strata which 

 burn to a white substance. I have also examined a strongly 

 impregnated mineral water, which exudes during wet weather 

 from the coal when stacked on the surface. Had my chem- 

 ical knowledge been greater, I should more accurately have 

 analyzed them ; as it is, I have only been able to detect some 

 of their ingredients, without minutely ascertaining their pre- 

 cise qualities. But I believe I can prove, nevertheless, that 

 they do contain many substances, which, under proper treat- 

 ment, may be rendered available. Of these the chief is sul- 

 phuric acid, the presence of which I have detected in all; 

 and, as is the case in gypsum, this is valuable by arresting 

 ammonia when brought into contact with it. Before we can, 

 however, with safety apply these refuse substances to heaps 

 of manure, we must endeavour to ascertain the nature of the 

 other ingredients, lest they should prove prejudicial. I think 

 I can show you that they contain both lime and iron ; in fact 

 the circumstance of the refuse burning to a red colour is 

 sufficient proof of the presence of the latter ; and the former 

 (lime) may be accounted for from the frequent recurrence 

 of fossil shells, which are composed of lime; — [a specimen 



