Scientific Intelligence, — Geology and Mineralogy. 367 



us from Copenhagen. It is on four sheets, upon a scale of jy^VffT* 

 and is highly creditable to the late Colonel Olsen, the superin- 

 tendent ; Professor Gunnlaugson, the draughtsman ; and Messrs 

 Scheel and Frisak, who conducted the triangulation. This is, 

 without doubt, the most important contribution to the exposition 

 of the natural condition of Iceland that has yet appeared ; and 

 therefore it is that I may dwell a moment longer on it than I 

 would upon works of a more common order. AH the prominent 

 natural features appear with great distinctness; and by a peculiar 

 hatching and tinting, the lava currents, heaths, moors, swamps, and 

 other peculiarities of surface, are well shewn, among which are those 

 enormous masses of ice (Jdlder)^ of more than 200 square miles 

 each, in different parts of the country. This really beautiful map 

 is founded upon the government surveys, executed at the commence- 

 ment of the present century, the elements of which have been sub- 

 jected to a new and careful recalculation. It is accompanied by an 

 index map on one sheet. An excellent work upon Iceland, by Dr 

 Schleissner, published by command of the Danish Government, and 

 presented to us by its talented author, ought also to be mentioned. — 

 Journal of the Royal Geographical Society^ vol. xx., 1850, Parti., 

 p. xlviii. A copy of this very beautiful and interesting Map has 

 just reached us. — Ed. of Edin. New Phil. Journal. 



3. Analysis of Gurolite, a new Mineral, by Dr T. Anderson. — 

 The mineral described and analysed by the author was found at 

 Stow, in Skye, where it occurs associated with apophyllite, stilbite, 

 and other zeolitic minerals. It is found principally in a compact 

 basalt, different from that in which these minerals are most abun- 

 dant, and which appears to have been produced by a different eruption 

 of basaltic matter. 



Gurolite occurs in the form of radiated crystalline masses with a 

 fine lustre. It cleaves readily parallel to the plates of which the 

 concretions are composed, and its hardness is about 3. Before the 

 blow-pipe alone it swells up, loses water, and finally fuses with some 

 difficultv into an opaque glass. Its analysis leads to the chemical 

 formula' 2 (Ca O Si O3) + 3 HO. 



The author referred to the relations which this mineral bears to 

 the other silicates of lime, of which three are already known, the 

 names and formulae of which are as follows : — 



Wollastonite (tabular spar), 2 Ca 3 Si O3. 

 Kalk-trisilicat of Gjelleback, Ca O Si O3. 

 Gurolite, . . . 2 (Ca Si Og) + 3 Ho. 



Dysclasite, . . ' . 3 CaO 4 Si 03-f 6 Ho. 



It thus appears that gurolite is the same silicate of lime as the 

 kalk-trisilicat, in union with water, and that its relation with 

 dysclasite is such that two equivalents of gurolite differ from one of 

 dysclasite by a single equivalent of lime only. 



