August 2, 19 17] 



NATURE 



447 



IXDIAN SALTPETRE.' 



THE brochure before us, issued by the Agri- 

 cultural Research Institute, Pusa, is the 

 work of the Imperial Agricultural Bacteriologist, 

 and is an interesting and valuable account of an 



FiJ. I. — A nufiiah's factory. Froqi Bullttin No. 68, Agricultural Research Institute, Pusa. 



important village industry, which, as is well and straw, 

 known, has long been carried on in various dis- 

 tricts of India where the factors determining the 

 formation of p)Otassium nitrate, as a soil con- 

 stituent, are sufficiently 

 favourable. These factors, as 

 summarised by the author, are : — 

 (i) Nitrifiahle organic matter 

 in suitable proportion in the 

 soil. 



(2) Lime. 



(3) Water, not only in suffi- 

 cient amount for nitrification, but 

 also distributed in the soil in such 

 a way as not to interfere witl 

 aeration, and to provide for con- 

 tinual capillary rise to the sur- 

 face. 



(4) Soil of such a texture as to 

 allow of continuous upward 

 movement of water from the sub- 

 soil to the surface. 



(5) Climate ensuring a provi- 

 sion of adequate moisture and 

 temp>erature during part of the 

 year and complete, or nearly :' 

 complete, absence of rainfall, i- ,. 

 coupled with low humidity during fig 

 a sufficiently long period to en- 

 sure the capillary rise of subsoil 

 water consequent on rapid surface 

 tion. 



The methods employed by the nuniah, as the 



1 "Saltpetre : Its Origin and Extraction in India." By C. M. Hutchinson. 

 Bulletin No. 68 of the Asricultiiral Research Institute, Pusa. (Calcutta : 

 Govemmenl Printing Offic, 1917.) 



NO. 2492, VOL. 99] 



operator is termed, for extracting saltpetre from 

 the surface layer, or calcareous portions, of the 

 alluvium have been frequently, although not 

 always accurately, described. Mr. Hutchinson 

 has studied these methods in detail, and his obser- 

 vations throw considerable light 

 upon a procedure which shows 

 little variation throughout India 

 and is based upon the accumu- 

 lated experience of generations of 

 predecessors. 



The supply of saltpetre is 

 almost entirely obtained from the 

 soil in the immediate neighbour- 

 hood of human habitations, or of 

 abandoned village sites where 

 nitrogenous organic refuse, con- 

 sisting largely of excrementitious 

 matters of men and animals, has 

 accumulated. 



The surface-soil, or chhilua, 



scraped to the depth of a quarter 



of an inch, is mixed with an equal 



quantity of residual earth from 



previous extractions, known as 



bhinjua, and is placed by treading 



into a circular filter-bed, or 



kuthia, consisting of a mud wall 



and floor plastered with clay, and 



having a bottom layer of bamboos 



Water is poured over the earth and, 



percolating through the loosely compacted soil, is 



collected in an earthen vessel. The first runnings, 



or murhan, contain most of the nitrate, mixed, of 



. — Treading the earth into the kuthia for extraction. From Bulletin No. 68, Agricultural 

 Research Institute, Pusa. 



evapora- 



course, with a greater or less quantity of common 

 salt. The solution is concentrated to the crystal- 

 lising point by boiling in an open pan over a fire 

 of dead bamboo leaves, the ashes of which, being 

 rich in potash, areiadded to the extracted earth, or 



