The Rev. S. Haughton's Notes on Mineralogy. 117 



If we take 314 for tlie atomic weight of stilbite, which accords 

 with its usual composition, we find the following — 



Mineralogical Composition . 



Quartz .... 7"33 ^ 



Felspar .... 6.2-55 

 Stilbite .... 29-83 



99-71 



It would be very desirable that an investigation similar to the 

 foregoing were made into the composition of the different varieties 

 of the vast and heterogeneous family of trap rocks. The nomen- 

 clature of this class of rocks is a reproach to geological science; 

 and no satisfactory classification can ever be made of these rocks 

 which is not based on their chemical and mineralogical, as well 

 as on their physical properties. Why should not such a body 

 as the British Association undertake the task of reducing to order 

 at least the British varieties of igneous rocks ? The funds requi- 

 site for the investigation could easily be procured, and the zeal 

 of the members of the Association would supply specimens from 

 every locality of interest : and certainly an authorized nomen- 

 clature of igneous rocks proceeding from such a source would 

 carry with it a weight which would go far to establish uniformity 

 of language and precision of ideas on this important, but ne- 

 glected, subject among British geologists. 



Let us take, for an example, the term clinkstone. This is a 

 name given from a physical property common to it with many 

 other rocks, including even limestones. The term was one 

 formed in the infancy of geology, and has come to be used in a 

 sense much more restricted than its original application ; it now 

 signifies a fine-grained fclspathic rock, of conchoidal fracture, 

 generally of a grayish colour, and containing zeolites as well as 

 felspar. This is the correct meaning of the term clinkstone; 

 and yet it is constantly applied to rocks which contain no zeo- 

 lites, and some of which arc not even of eruptive origin. This 

 confusion as to the meaning of the term has led to the use of 

 various synonyms, or quasi synonyms, of which it is sufficient 

 to mention felspathic trap, hornstone and felstone, — the latter 

 recently revived very usefully by the Government geological sur- 

 veyors. Why should not all these terms, if retained at all, be 

 used in definite senses ? The republic of geologists is small, and 

 many of its citizens arc well educated ; surely there could be no 

 great difficulty in getting them all to use the same language. 



Triuity College, Dublin, 

 January 14, 1857- 



