3S IMKlV (JIKNSKL 



Cochcrane brought from the siiniiiiit (1.500 feet) a piece of black porous lava; 

 and uiuler it lie foiiiul some dark iiardened clay full of cells, the inside of which 

 appear sli^litly \ itritk-d. The ishuul seems chiefly composed of this porous lava; 

 the strata of which, beini; crossed at ri^ht an^^les by a very compact black lava, 

 dij) on tile eastern side of the island about 22' and on the west side l6°, pointing 

 to the centre of tiie island as an apex" (l, j). 198). 



In 1S30 C\ Hi:kii:r<» j^ublished some observations under the title 'Notice 

 sur rilistoire naturelle de file juan hV-rnandez'. With regard to geological ques- 

 tions he sa\s: "je pense ciu'un geologue n'y trouverait cjue du basalte dans les 

 etats, lueiue dans cehii de la j)lus parfaite decomposition; plusieurs blocs sont 

 parsemes dune cristallisation j)articulicre, a laquelle on donne, je croix, le nom 

 d()li\ine ... 11 n'\- a pas de trace de volcan ; les pierres qu'on prend pour 

 de la hue, et dont (iuel(|ues-unes ressemblent assez aux scories on de la pierre 

 j)once. ne sont, a mon avis, (jue du basalte decompose; on trouve aussi cette 

 rociie sous forme sj)hericiue. et composee de couches concentriques ..." (2, 

 p. 34;; compare in the latter respect h^ig. 10 on page 52 of this paper). 



.\. (Ai.ix i.Kic;!!, who accomj)anied Captain P. Parker Kixc; on the sur- 

 \f\ing \()\ages of II. M.S. Adventure and Beagle on their first expedition 

 1S26 1S30, read before the (Geological Society of London on Jan. 5th, 1831, a 

 statement on 'The geology of the island of Juan Fernandez'. In the Proceedings 

 of that N'ear the following account of Caldcleugh's discourse is given: "The 

 author could discover no trace of a volcano, said to exist here by former visitors; 

 all the rocks, according to him, consist of basaltic greenstone and trap of various 

 mineralogical structure, both amorphous and vesicular, together with trappean 

 concretions, no other contained minerals being observable except olivine and 

 chaux carbonatee metastaticpie. It is further mentioned that the basalt in parts 

 is almost colunuiar, and in others has a [)eaked and serrated outline, the mass 

 being, here and there, traversed by dykes. Owing to the peculiar character of 

 this basalt, and especially from the great quantity of olivine, the author compares 

 its age with that of the basalt of Bohemia, the Rhine, the Vivarrais and Beaulieu 

 in Provence ' (3, p. 256, also i)uhlishe(l in the Phil. Mag. and Annals of Philosophy, 

 \'ol. l.\, I S3 I, }). 220). 



Captain King recaj)itulates Caldcleugh's narrative, as given above, with the 

 addition: "In captain llAi.i.s interesting journal, there is a list of geological and 

 mmeralogical specimens, of which one from Alasafuera is named vesicular lava" 

 I4. p. 304). '1 he uhimate destiny of these specimens is unknown. 



Members of tlie Dumont dl'rville expedition, when visiting Masatierra in 

 1S3S. collected and specified several different saiu})les of the lavas from the island 

 '-^- P- ■'4'- 1 he material tor the new analyses of basalts from Masatierra, which 

 L\(K<iix recentl\- caused to be made and which will be referred to later on, are 

 evidentlx- trom this collection, as Lacroix says they were made from specimens 

 collected by the Dumont dCrMlle exj)edition. G. (iUANCiK records some observa- 

 tions as tollows: "Toutes les roclies aj)j)artiennent a diverses varictes de trapp 

 et de diorite basaltique amorphes et vesiculaires, on ne trouve dans ces roches 

 volcanicjues aucun autres mineraux (jue de I'olivine et de la chaux metastatique. 



