1T387, 388. 889] black pebble— chalybeate springs. 215 



energy, takes place at times, more or less, in most or all soils, when, in long wet 

 seasons, they are temporarily in an und rained condition. Nevertheless, we 

 find an exception to the rule above re 'erred to, in the case of the soil and subsoil 

 of the Marshall County Table lands (see table No. 2) in which the surface soil 

 is richer in iron than the subsoil; a proof of the perfe:t natural thorough -drain- 

 age of some of these soils. 



387. Bog Ore, or ''Black Pebble." — When light and open soils possessing a 

 porous subsoil, underlaid, in its turn> by denser strata, are placed under 

 conditions like those referred to above, an effect is produced which is very 

 familiar in some regions of this State, and of which examples on a small scale 

 may be found in most neighborhoods. Soils of the character just mentioned, 

 being but very slightly retentive of soluble matters of any kind, will allow any 

 solution of iron formed in it to sink, until it reaches a denser stratum, where it 

 is retained and gradually forms bog ore or "black gravel," while the surface soil, 

 being deprived of its coloring elements (iron, a^ well as vegetable matter), 

 becomes light gray or almost white, in strong contrast to adjoining bodies of well 

 drained, yellow loam land. It is probable that this process of lixivation extracts 

 from i he soil other and more valuable ingredients {e.g. phosphoric acid), besides 

 the iron and vegetable matter, and it is, perhaps, for this reason, that these white 

 or ,; crawfishy" soils are, with few exceptions, less productive than those from 

 which they were forme I by the combined action of vegetable matter and stagnant 

 water. The difference is plainly exhibited, in most cases, by their natural 

 vegetation, which, though otherwise widely distinct in different localities, 

 possesses one element of almost constant occurrence, to-wit : stunted Huckle- 

 berry bushes. The Flatwoods of N. E. Mississippi, and the bottoms of South 

 Mississippi, often exhibit examples of this kind on the large scale. Some soils 

 of this character are, nevertheless, very productive when properly drained and 

 supplied with vegetable matter ; and in many cases which have come to my 

 knowledge, the application of lime to them has proved extre.nely beneficial. 

 As yet, however, no analyses of this class of soils, from which their character- 

 istics coold be deduced, have been made. 



388. From the foregoing considerations, it will be appa - ent how great is the 

 importance of thorough drainage in lands strongly charged with peroxide of 

 iron, or iron rust, as are a large portion of the best uplands of the State. Not 

 only are the solutions of iron, so readily formed in such soils when undrainel, 

 a positive poison to plants, but, while the partial withdrawal of iron alone 

 would be no disadvantage to the soil, the process upon which its solution depends, 

 drafts largely upon that important ingredient of the soil, its humus or vegetable 

 ma'ter ; as well as, probably, upon several other important elements, and 

 among these, especially upon the Phosphoric acid. The "black pebble" or bog 

 ore, which owes its formation to this process, is well known to be particularly 

 rich in the latter substance — for which reason, though unfit for the manufacture 

 of malleable iron, it is preferred for such metal as is to serve for fine castings. 



38!). Chalybeate Springs. — A phenomenon dependent upon the sanre cause, 

 intrinsically of much less importarrcc, but which has frequently attracted 

 attention and excited curiosity in this State, is found in the diminution or dis- 

 appearance of the mineral ingredients of chalybeate springs, so soon as the spots 

 on which they were situated were "improved." or the springs themselves 

 cleaned out. The ferruginous sands of the Orange Sand formation (UlO) give 

 rise to a great number of chalybeate springs (If 75), many of which have no other 

 origin than this : that the decaying vegetable mattercollected in depressions of the 

 surface, heads of hollows, etc., or even in the basin of the spring, effects the 

 transformation above re'erred to, i. e. of the insoluble iron rust into soluble 

 •carbonate of the protoxide, which passes into the spring water, rendering it 

 chalybeate. It follows as a matter of course, that so soon as the vegei able 

 matter which causes this transformation is removed, the water must lose its 

 mineral ingredients. This, however, can only happen to superficial springs, 



