354 



On Nitrate of Soda. 



tain common salt, sulphate and carbonate of soda, muriate of lime, and occa- 

 sionally some borate of lime is found under the nitrate-beds. 

 ■* " Fragments of shells have been noticed with and under the nitrate-beds. 

 Mr. Blake mentions that 200 feet above the pampa (which is 3500 above the 

 sea), near to Los Salitres del Porte, limestone containing shells rises from abed 

 consisting of pebbles and shells cemented together by salt and nitrate of soda. 

 Part of the shells are decomposed, whilst others are perfect in form, and 

 resemble those now still found living on the rocks in the inlets of the sea." 



He brings us further the satisfactory news that 



" The Pampa de Tamarugal contains sufficient nitrate for the consumption 

 of Europe for ages ; the desert of Atacama yields it ; it has also been met 

 with in the Andes and in the eastern plains." 



Darwin, in the short account of his hasty visit, observed, as 

 a geologist, on the nitrate band : — " The stratum follows the 

 margin of a grand basin or plain, which manifestly must once 

 have been either a lake or inland sea. The elevation at present 

 is 3300 feet above the Pacific." The assertion will not startle 

 those who are acquainted (and who is not?) with Sir Charles 

 Lyell's great work, demonstrating that sea and land are ever 

 gradually changing place, by an imperceptible rise or lowering 

 of the land's level during the revolution of countless ages. This 

 coast, indeed, is well known for signal upheavals in our own days. 

 Southwards the famous earthquake of 1822, described by an 

 eyewitness, Lady Callcott, raised the entire line of coast near 

 Valparaiso four feet out of the sea; and again, in 1835, another 

 earthquake lifted the island of St. Maria ten feet ; while north- 

 wards, near Lima, is found the dry bed of a river once used for 

 irrigation, the marks of cultivation being still visible on the side, 

 but this bed now stands ffti/ feet higher than the present stream, 

 which an earthquake has diverted into a new channel adjoining. 

 Such a change having visibly happened since Peru has been 

 inhabited, it is more easy to conceive, what no geologist indeed 

 doubts, that the whole plain of Tamarugal has been raised from 

 beneath the waves to its present height in the innumerable lapse 

 of ages. 



The occurrence therefore of common salt-beds on the deserted 

 bottom of a sea which has slowly evaporated and finally dis- 

 appeared would present no difficulty. Such superficial salt-beds 

 indeed are by no means uncommon. They are found also near 

 the Caspian Sea, and on the eastern coast of South America, as 

 well as the western. In the neighbourhood of Iquique a similar 

 bed is now actually being formed by the side of the ocean. Mr. 

 Bollaert describes it thus : — 



" In a plain near the Ansuelo rock at Iquique, and some 1000 yards from 

 the shore, seawater is found near the surface. At the margin of the 

 beach there is a sandy ridge or elevation, behind which the land is depressed. 

 It is in this depressed part the seawater is found near the surface, where it 

 readily evaporates, leaving layers of salt. Spring tides will add to this depo- 



