Steam Cnltnrc and Clay Soils 



117 



my farm generally has increased considerably 

 under steam culture; but, unlike Mr Smith, 

 I only grow corn crops on three-fifths of 

 the farm, the remaining two-fifths being under 

 green crops. 



At the present time, on land which cannot 

 be classed as root land, I have as good a 



plant of mangolds, swedes, and turnips as can 

 be found in England. 



I cannot do better than close my lettei" 

 with saying to all who are sufficiently 

 interested in the question of what the clay- 

 lands of England may be made to do, let 

 them go to Woolstone and see. 



THE CHILI SALTPETRE DEPOSITS OF PERU. 



IN travelling eastward through Peru, from 

 the sea to the Cordilleras, on the 20th 

 parallel of south latitude, seven zones are 

 crossed, the third of which, the Pampa of 

 Tamarugal, and the fifth, Serrania Alta, or the 

 inner chain {Upper Peru, or Bolivia), are ex- 

 plored for saltpetre. The treeless Pampa, a 

 plain somewhat depressed in the centre, has 

 a very scanty vegetation, and the only thing 

 which grows there is a single variety of lu- 

 cerne grass (mendicago) ; the cultivation ot 

 even this is attended with difficulty, on ac- 

 count of the large proportion of common salt, 

 borax and saltpetre in the soil. It serves in 

 part for the support of the beasts of burden 

 used for transporting to the coast .the salts 

 and metallic minerals found here. In the 

 south of the Pampa is a large deposit of bo- 

 rax, pieces of which weigh on an average from 

 100 to 200 grimmes : soda saltpetre is found 

 on the borders of Pampa and Serrania, but 

 too far distant from the sea. On the 

 western slope of the Cordilleras, salt is 

 only found in small quantities ; but in Upper 

 Peru, where frequent rains wash it together 

 into great lakes, there are large quantities of 

 it. The saltpetre mines consist of different 

 strata. The surface of the ground is com- 

 posed of silicates,sandstone,and pieces of lime. 

 At a depth of from 8 to 1 6 inches, very regular 

 prisms are usually found, which sparkle with 

 a mass of very small microscopic crystals ; 

 the strata below this, which is of rocky hard- 

 ness, consists principally, of common salt, 

 with a little chloride of potassium and soda 

 saltpetre, mixed with earth and pieces of 



of silicates and carbonates, and has a thic'^-. 

 ness of 20 to 25 inches. Beneath this crust 

 is the pure soda saltpetre, m more or less 

 perfect crystals, from 20 to 40 inches long 

 and 3 to 7 feet in diameter.. Guano is sel- 

 dom found there, and only in small quanti- 

 ties ; and it always occurs just below a stra- 

 tum of salt. It is not in a powder, like that 

 from the Chincha Islands, but adheres 

 together, and is of a brown colour, contain- 

 ing the bones and remains of birds and> 

 insects, and has an ammoniacal smell. 



The chloride of sodium and lime present 

 furnish mineral constituents required for the 

 formation of the saltpetre. According to 

 Thiercelin, the guano furnishes the nitrogen; 

 but since the guano is always found below 

 the salt crust, Kosnig is compelled to refer 

 the nitrogen to some other nitrogenous or- 

 ganic bodies, from whose decomposition am- 

 monia is formed, and this in turn is con- 

 verted by the action of the air and organic 

 bases into nitric acid. Besides the three 

 substances named, all the conditions favour- 

 able to the formation of saltpetre are found 

 in that neighbourhood, namely, a pure dry 

 atmosphere, absence of rain to wash away 

 the saltpetre when formed, and the regular 

 night fogs. The latter, leaving the salt un- 

 dissolved, dissolve the saltpetre, and filter it 

 through this stratum, under which it crystal- 

 lizes. 



The search for saltpetre is conducted thus : 

 — The workman recognizes its presence by 

 certain undulatory elevations of the ground, 

 and numerous lumps of lime and disinte- 



