304 Scientific Proceedings, Royal Dublin Society. 



tion of the names it has received. I may as well state at once that, 

 as regards the last point, I have a strong objection to the naming of 

 minerals after places, particularly when named after small and 

 unknown localities. Thus Dana has named a fine-grained mixture 

 of galena and blende Huasolite, from the province of Huasco, where 

 it was found. Even here, I am of opinion that such terms are not 

 desirable, if we wish to inculcate the idea that thej are distinct 

 species. A province, however, is generally well known, and it is 

 quite different to Kilmacoo — a local name, not even to be found 

 in any published gazetteer or postal directory. The objection 

 would be obvious, because until we got " Kilmacooite" recognized 

 in the text-books upon mineralogy, the man of science would be at 

 a loss to know what that name meant, or even to trace its con- 

 nexions. There is also as great an objection to the term " Blue- 

 stone," the name used by the miners in Wales. The mineral is of a 

 steel-grey colour, not blue ; and, besides, this term is applied to a 

 well-known chemical substance. I therefore prefer to call it 

 argentiferous galenetic blende. 



I view the mineral as an intimate mixture of fine crystals of 

 galena and blende, which, although they form a fine-grained sac- 

 chorid mass, apparently homogeneous to the eye, I have no hesita- 

 tion in saying is composed of a mechanical mixture of microscopic 

 crystals of two minerals. When treated with dilute nitric acid, 

 the blende seems to be attacked first, but I do not attach much 

 importance to this fact. If, however, we powder some of the 

 mineral and examine it under the microscope with an inch object- 

 glass, and strongly illuminate it with transmitted light alone, we 

 find that about two-thirds of the particles transmit light, whilst 

 the others do not. Now, galena owes its strong metallic lustre 

 to its great opacity, and I think we are justified in pronouncing 

 that these last particles are galena, and that those which transmit 

 light are blende. The finest film of galena that can be got by acting 

 upon an alkaline solution of lead oxide with thio-urea does not 

 transmit light, whilst blende obtained artificially by a similar 

 method is quite transparent. 



I do not think the analysis in Mr. Argall's Paper could represent 

 very pure specimens of the minerals. It will be observed that the 

 samples procured by me are very uniform in character, except a few 

 isolated crystals of pyrites, which can be perceived with the eye. 



