278 HEALTH ON THE CALCAREOUS PRAIRIES. 



the experience of every unhealthy town which has suffered much 

 from fire. If a fair estimate is made of the immense quantity of 

 mild calcareous earth which is contained in the plastering and 

 brick-work of even the wooden dwelling-houses of a town, and still 

 more of those built of masonry, it -must be admitted that all that 

 material being separated, broken down (soon or late), and spread, by 

 the burning of the houses and pulling down their ruins, is enough 

 to give a very heavy cover of calcareous earth to the whole space 

 of land burnt over. It is to this operation, in a far greater degree 

 than to all others, that I attribute the beneficial effects to health 

 of the burning of towns. 



I proceed to the facts derived from the extensive body of prairie 

 lands in Alabama which rest on a substratum of soft lime-stone, or 

 rich indurated clay marl. It was from these remarkable soils that 

 the specimens were obtained which were described at pp. 66, 67. 

 Some of these, indeed all that have been examined by chemical 

 tests, of the high and dry prairie lands, contain calcareous earth 

 in larger proportions than any soils of considerable extent in the 

 United States that I have seen or tested. The specimens not con- 

 taining free calcareous earth are of the class of neutral soils ; and 

 the calcareous earth, which doubtless they formerly contained, and 

 from which they derived their peculiar and valuable qualities, may 

 be supposed only to be concealed by the accumulation of vegetable 

 matter, according to the general views submitted in Chapter VII. 



The more full descriptions of the soils of this remarkable and 

 extensive region before referred to render it unnecessary to enlarge 

 much here. It will be sufficient to sum up concisely the facts there 

 exhibited, and which agree with various other private accounts 

 which have been received from undoubted sources of information. 

 The deductions from these facts, and their accordance with the 

 theory of the operation of calcareous matter, are matters of rea- 

 soning, and, as such, are submitted to the consideration and judg- 

 ment of readers. 



The soil of these prairie lands is very rich, except the spots 

 where the soft lime-stone rises to the surface, and makes the calca- 

 reous ingredient excessive. In the specimen formerly mentioned, 

 the pure calcareous matter formed 59 parts in the 100 of this 

 " bald prairie" land. The soil generally has so little of sand, that 

 nothing but the calcareous matter which enters so largely into its 

 composition prevents it being so stiff and intractable, that its tillage 

 would be almost impracticable. Yet it is friable and light when dry, 

 and easy to till. But the superfluous rain-water cannot sink and 

 pass off, as in sandy or other pervious lands, but is held in this 

 close and 'highly absorbent soil, which throughout winter is thereby 

 made a deep mire, unfit to prepare for tillage, and scarcely practi- 

 cable to travel over. This water-holding quality of the soil, and 



