8G GEOLOGICAL RECONNOISSANCE 



A peculiar fatty or oily principle seems to be extracted with the nitre- 

 salts, during the leaching of the earth, which, according to J. S. Thompson, 

 rises in the form of a greasy scum to the surface, during the progress of 

 the evaporation, and is capable of saponification with alkalies. 



The quantity of organic matter was too small, in the amount of earth 

 subjected to qualitative examination in the laboratory, to be appreciable ; 

 we are, therefore, still left to conjecture, from the accounts given of the 

 nature of this substance, what it may prove to be. If it is capable of form- 

 ing a soap with lye, as represented, we should suppose it to be one of the 

 oily acids ; but, as these are insoluble in water, they could not be taken up 

 by the water used to extract the soluble salts from the earth in their un- 

 combined state, as this fatty principle seems to have been ; nor do we un- 

 derstand how it could be so readily washed off the hand by simple water, 

 as we understand the substance in question to have been. Glycerine, it is 

 true, is a component of many fats, which, when set free, is miscible with 

 water ; but this is a basic, organic compound, which does not form true 

 soaps ; neither has it the greasy feel which the substance contained in the 

 nitre-earth is said to have. It is more probable that it may be some com- 

 bination of one of the known oily acids, with ammonia, which is soluble 

 in water, as a kind of ammoniacal soap ; from this, when subsequently de- 

 composed by the addition of lye, the ammonia may be set free, while the 

 stronger alkali, taking its place, combines with the fatty acid to form a 

 soap, which finally rises to the surface, when the liquor becomes sufficiently 

 concentrated. This is rendered more probable, since by the addition of 

 caustic lye to this earth, ammonia is evolved. 



It seems likely that the animal matters, present in this earth, may un- 

 dergo a gradual change in their native bed, similar to that which pro- 

 duces adipocere, but resulting in the combination of margaric, or some of 

 the other oily acids, with ammonia, which is more soluble in water than 

 that substance. 



We have several pounds of this earth still on hand, and may be able, 

 hereafter, to determine the nature of this organic principle, if it exists in 

 sufficient quantity to be separable, so that it can be subjected to the neces- 

 sary tests for its determination ; if not, we must trouble Mr. Thompson to 

 collect, the next time he has occasion to make saltpetre, some of this sub- 

 stance from his kettles, for future special investigation. 



About a mile below J. S. Thompson's, an escarpment of silico-calcareous 

 beds runs along the western borders of Cave creek, the lower layers of 

 which, decaying faster than the superincumbent mass, have formed a deep 

 recess beneath overhanging ledges. One of the early settlers in this part 



