282 CALCAREOUS MANURES— APPENDIX. 



waters have been withdrawn, as stated above, the country is again a desert, 

 and the former habitations are tenantless ruins. Another inhabited and culti- 

 vated spot in the desert is afterwards thus mentioned. "The country around 

 Shurukhs is well watered with aqueducts, from the rivulet of Tejend, which 

 is a little brackish, but its waters are usefully employed in fertilizing the 

 fields. The soil is exceedingly rich, and possesses great aptness of agricul- 

 ture ; the seed is scattered and vegetates almost without labor. The harvest 



is rich." "The inhabitants repeat a tradition that the first of men tilled 



in Shurukhs, which was his garden, while Serendib or Ceylon was his 

 house ! There is not a tree or a bush to enliven the landscape." 



But these speculations, however plausible, would require many additional 

 facts and proofs, to place them on as sure ground, as I flatter myself, the 

 earlier part of this essay has done for the cause of the formation of prairies. 

 However interesting it may be to the inquiring mind to extend views so far 

 upon unexplored ground, prudence admonishes that in that way I have al- 

 ready exceeded the proper limits of argument sustained by known and 

 undoubted facts. 



Addendum. 



Since the first publication of this piece (in 1835) there have come under 

 my notice many statements of facts serving to confirm the positions as- 

 sumed, and none to oppose them. Most of these statements are of more 

 extended observations of other prairie soils and prairie regions, which are 

 unnecessary to recite, as they agree generally and fully with the numerous 

 particular examples cited in the foregoing pages. Some otlier of such 

 evidences, on a different branch of the subject, will be here added, in con- 

 firmation of some of the positions before presented. 



It was stated above, on the authority of Denon, that the soil of part of 

 the sandy desert of Egypt (near Lycopolis) which is encroaching on and 

 covering the rich borders of the Nile, consists of almost pure carbonate of 

 lime, in calcareous sand formed by the continual disintegration of the range 

 of Lybian mountains, there close adjacent. Also, on general authority 

 and understanding of the facts, that this calcareous sand, though forming 

 a barren and naked desert when dry, -vas made fertile wherever moistened 

 naturally or artificially, by the waters of the Nile. Other facts were stated 

 of places which are now and have long been naked deserts of dry sand, 

 which are known to have been formerly watered by the industry of man, 

 and were then highly fertile. And hence my inference that, wherever 

 watering of barren sands had induced fertility, such sands must have 

 been highly calcareous; and that the great abundance of the calcareous 

 ingredient is both a cause of the barrenness of such soils when dry, and of 

 their immediate change to productiveness and subsequent great fertility, 

 when supplied with water. If, (to suppose a case.) instead of 70 per cent, 

 of finely divided carbonate of lime in the soil of what is now a desert, there 

 had been but 10 percent, of that ingredient, and all the other parts had 

 been silicious sand and clay, it may be presumed that the land would be 

 much less barren than it is in these highly calcareous deserts, and with 

 a moderate share of rain might be actually and highly fertile. In Egypt 

 rain is a very rare occurrence; and therefore, except where watered 

 naturally or artificially from the Nile, the highly calcareous sands are with- 

 out moisture, and must necessarily constitute a perfectly barren desert. 



The Lybian mountains being composed of calcareous rock, continually 

 disintegrated and blown away by the winds in fine sand, would also alone 

 serve to prove that the vast extent of desert sand thus spread over Egypt 



