SALT- WORKS OF ARAYA. 
187 
recent sandstone*, and lastly, sometimes in a gypsumf pos- 
terior to tlie chalk. 
The new salt-works of Araya have fire reservoirs, or 
pits, the largest of which have two thousand tlrree hun- 
dred square toises surface. Then* mean depth is eight 
inches. Use is made both of the rain-water, which by 
filtration collects at the lowest part of the plain, and of 
the water of the sea, which enters by canals, or martellieres, 
when the flood-tide is favoured by the winds. The situa- 
tion of these new salt-works is less advantageous than that 
of the lagoon. The waters which fall into the latter pass 
over steeper slopes, washing a greater extent of ground. 
The earth already lixiviated is never carried away here, as 
it is from time to time in the island of Margareta ; nor have 
* At Punta Araya. 
t Gypsum of the third formation among the secondary gypsums. The 
first formation contains the gypsum in which are found the brine-springs 
of Thuringia, and which is placed either in the Alpine limestone or 
zeehstein, to which it essentially belongs (Freiesleben, Geognost. Arbeiten, 
tom. ii. p. 131), or between the zeehstein and the limestone of the Jura, or 
between the zeehstein and the new sandstone. It is the ancient gypsum 
of secondary formation of Werner’s school (alterer flozgyps), which we 
almost preferably call muriatiferous gypsum. The second formation is 
composed of fibrous gypsum, placed either in the molasse or new sand- 
stone, or between this and the uppor limestone. It abounds in common 
clay, which differs essentially from the salzthon or muriatiferous clay. 
The third formation of gypsum is more recent than chalk. To this 
belongs the bony gypsum of Paris; and, as appears from the researches of 
Mr. Steffens (Geogn. Aufsatsze, 1810, p. 142), the gypsum of Segeberg, 
in Holstein, in which sal-gem is sometimes disseminated in very small 
nests (Jenaische Litteratur-Zeitung, 1813, p. 100). The gypsum of 
Paris, lying between a cerite limestone, which covers chalk and a sand- 
stone without shells, is distinguished by fossil bones of quadrupeds, 
while the Segeberg and Lunebourg gypsums, the position of which is 
more uncertain, are characterized by the boracits which they contain. 
Two other formations, far anterior to the three we have just mentioned, 
are the transition gypsum (ubergangsgyps) of Aigle, and the primitive 
gypsum (urgyp.s) of the valley of Canaria, near Airolo. I flatter myself 
that I may render some service to those geologists who prefer the know- 
ledge of positive facts to speculation on the origin of things, by fur- 
nishing them with materials from which they may generalize their ideas 
on the formation of rocks in both hemispheres. The relative antiquity 
of the formations is the principal object of a science which is to render 
us acquainted with the structure of the globe ; that is to say, the nature 
of the strata which constitute the crust of our planet. 
