12 Transactions of the Kansas 



found to afford 5.35 per cent, of sulphuric acid in tlie form of the freely soluble 

 sulphates of iron and aluminum. 



Thus we have in the chemical constitution of this hot bluff a perfect explanation 

 of the startling phenomena which are there occurring. Below, a rock largely con- 

 sisting of earthy carbonates freely decomposable by tlie presence of free acids. 

 Above, a series of layers completely charged with an abundance of this free acid. 

 When, by the scaling off of the face of the bluff, these agents are intimatelj- mixed 

 in an immense mass of thousands of tons of debris the free acid immediately 

 attacks the easily yielding carbonates with great violence, and a "hot bluff" very 

 naturally springs at once into existence. The intense degree of heat produced,, 

 however, is from another and more complex cause than this. If the simple acid 

 shale were by itself without the limestone, piled in a large heap, and water added, 

 there wo'uld be a very rapid rise of temperature within from tlie greatlj^ increased 

 rapidity with which the process of the oxidation of the iron pyrites would go on 

 under these circumstances. It is well known that in the shales of Whitby, Eng., 

 when thus piled and moistened with water, the oxidation of the pyrites will develop 

 so intense a degree of heat as to spontaneously set fire to the bituminous matter 

 which the shale contains. But when, as in the case of this Nebraska bluff, to the 

 heat generated by this rapid oxidation produced by increased exposure to air and 

 the water of the river and rains, tliere is added the violent avidity with which the 

 free sulphuric acid attacks the carbonates of lime and magnesium, the effect is 

 naturally powerful and startling in the extreme. 



Under these encouraging conditions many iuterestiug chemical compounds are 

 here in the process of formation. By the decomposition of the carbonate of cal- 

 cium by the sulphuric acid, magnificent crystals of Selenite (Gypsum), are now 

 forming in immense abundance. The crystals are exceedingly perfect and beauti- 

 ful ; many of them somewhat rare in form, long, slender, needle-shaped crystals, 

 but still perfect rhomboidal prisms with bevelled edges In some instances in the 

 solid mass of the blufi" itself, where the layers of the limestone and the acidified 

 shale are conjoined, there are formed seams of a half inch or more in thickness 

 completely filled with interradiating crystals of Selenite partiallj- coated with the 

 yellow hydrated oxide of iron. B}- the decomposition of llie magnesium carbonate 

 there is here formed magnesium sulphate or Epsom salts distributed over the rock 

 in a very minute incrustation of efllorescent crystals. 



Finally, by the slow decomposition of the argillaceous or clayey portions of the 

 rock itself there is produced the Sulphate of Aluminum in minute crystalline tufts 

 called on account of its form " Feather Alum." These last two compounds suggest 

 an economical phase of what has thus far been simply an exceedingly interesting 

 chemical phenomenon. It is well known that the great proportion of the common 

 alums are manufactured from shales almost identical in nature with those which form 

 the black seams of this Nebraska blufi". In the great English alum fields, for 

 example, the shale, full of partiall}^ decomposed jiyrites, is collected, piled in oblong 

 heaps, and slowly fired to completely carry out the oxidation which has been begun. 

 A large quantity of free sulphuric acid is thus produced which attacks the shale 

 forming Aluminum Sulphate. This is removed by leaching with water and the 

 addition of some available form of potash or ammonia is all that is needed to crys- 

 tallize out the common potash or ammonia alums of commerce. Now, in the case 

 of this Nebraska blufi', this oblong mass of heated debris bears no verj^ distant 

 resemblance to a " curing heap " of an alum manufacturer. The presence of the 

 limestone is, to be sure, most unfortunate, ;'nd would necessarily be avoided if the 



