Government Survey of Scotland. 367 



in accordance with the evidence he gave before the Parlia- 

 mentary Committee of 1851. 



We therefore confidently hope that the survey will now 

 proceed without further interruption and delays. We have 

 seen with great satisfaction that an additional grant of 

 £10,000 appears in the Ordnance estimates for this year, 

 making the grant for this year £35,000 for the survey of 

 Scotland — a sum which will enable the Ordnance officers 

 to proceed rapidly in their work, and give employment to a 

 numerous body of assistants from our population. E. 



On a Quartziferous Variety of Trachyte, found in Iceland. 

 By Theodor Kjerulf, of Christiania. Communicated for 

 the Edin. New Phil. Journal. 



Amongst the trachytic formations of Iceland, which appear 

 from the investigations of Bunsen to exhibit, along with the 

 greatest mineralogical differences, a remarkable chemical 

 agreement, and which, in a paper inserted in the twenty- third 

 volume of Poggendorff's Annalen, he terms " normal tra- 

 chytic," there are some which are characterised by the occur, 

 rence of interspersed quartz and rock crystal. These, as well 

 as the other trachytes of Iceland, belong to Abich's " tra- 

 chytic porphyries," with which they harmonize, not only in 

 their chemical comp6sition, but also in the circumstance of 

 their assuming, for most part, a porphyritic appearance by 

 the interspersion of minute lustrous lamella of felspar. In 

 the rocks referred to in the following paper, which belong to 

 these formations, these felspar secretions are absent, although 

 in them likewise the rock presents a porphyritic appearance, 

 from being interspersed with quartz. We might give it the 

 appellation of quartziferous trachytic porphyry. The mass 

 appears decomposed, almost friable, and in colour varying 

 from light green to yellowish red. In similar varieties of 

 trachyte, the mass being the same, but quartz being absent, 

 there could be distinguished small spicula of iron pyrites, 

 which seemed to indicate a subterraneous formation by the 

 disengagement of sulphureous vapours from fissures (Fumaro- 

 lenwirkung). In tlie present rocks, however, I could not, 



2 b 2 



