Prof. A. E. Nordenskiblcl — Geology of Spitzbergen. 125 



originally formed of limestone, have then sometimes the appearance 

 as if they had been burnt, but on a closer examination it is found 

 that the alteration arises from the limestone strata being impreg- 

 nated with silica. The altered appearance of the stratum, therefore, 

 originates rather from an infiltration of silica than from the action, of 

 heat. I consider it highly probable also that the immense flint 

 stratum — often containing shells of Productus, etc. — which occurs 

 in the Mountain Limestone formation, has the same origin as the 

 diabase beds. 



It is scarcely possible to consider these beds purely eruptive 

 formations, though I by no means deny that the veins of diabase 

 and probably also that which forms isolated rocks without ad- 

 mixture has broken out in a state of fusion from the interior of the 

 earth. It appears to me that the diabase strata can only be accounted 

 for by the supposition that they are composed of immense strata of 

 volcanic sand and ashes, which in the lapse of time were meta- 

 morphosed into a hard crystalline rock. It is possible, too, that 

 the gravel originating from the action of the atmosphere upon the 

 diabase which has thus been formed, may, under favourable circum- 

 stances, without intermixture of foreign matter, be collected into 

 strata of diabase sand,^ which sand, under circumstances favourable 

 thereto, may again be compacted into a rock not distinguishable 

 from that from which it originated. 



A pseudo-plutonic stratum of this kind may therefore be inter- 

 stratified with fossiliferous beds, deposited much later than the 

 material of the pseudo-plutonic stratum was thrown up from the 

 interior of the earth.^ 



1 Such strata of diabase sand also now occur in many places on the coasts of 

 Spitzbergen ; for example, in Hinloopen, off the Low Island, etc. 



2 I have before given expression to the view that the condition of a rock depends 

 much more on the composition of the original materials than on the mode of occur- 

 rence, and that a volcanic glass and a sediment of the same chemical composition, 

 after the lapse of immense periods of geological time, give the same ultimate 

 product, inasmuch as the molecules arrange themselves according to the most 

 favourable relation of equivalents; and as an instance showing that molecular 

 changes may take place in solid substances, I may point to iodide of silver, to the 

 changes produced in the form of sulphur crystals, and to iron which has been exposed 

 for a length of time to concussions (for instance, axles of railway waggons). I have 

 obtained besides two geological examples of such changes. The first I got from the 

 distinguished chemist Gentele, who, without knowing that he was contributing to the 

 solution of a disputed point of great importance in geology, some few years ago, sent 

 to the Eiks Museum a box of common light grey malakoiite, on account of the extra- 

 ordinary circumstance that the mineral when removed by blasting from the mountain 

 was amorphous, but soon after began to assume a coarsely crystalline structure. The 

 other was communicated to me by A. G. Nathorst, Decent in Geology at the Univer- 

 sity of Lund, whose attention, when he took part last summer in the geological 

 survey of Sweden, was directed by a farmer to a vein of calcspar which had under- 

 gone a change of texture from a compact to a crystalline state during a period of 25 to 

 30 yearn. I have wished to quote these cases so much the more because there is 

 no possibility that the observers have been led astray by a theoretic view previously 

 adopted. Those who are disposed to deny the possibility of a mass of the nature of 

 tufa being changed to a crystalline rock, ought besides to keep in view that, 

 according to all experience, a melted mass of silica cools to a glass, and that therefore 

 for the purely eruptive diabase we also must suppose that an inward molecular change 

 did take place after the soHdification of the rock. 



