348 Scientific Proceedings, Royal Dublin Society. 



their limestone equivalents in the Irish Cambro- Silurian eurites ; 

 while the "lay and lay" are like the " shells of limestone " that 

 are not uncommon in the county Donegal Cambro- Silurians — an 

 apatite vein or a limestone vein with only one wall "makes" exactly 

 similar. I could not satisfactorily find out if, in any place in the 

 regular lodes, the apatite changed entirely into calcite [I was too 

 weak and giddy after my recent illness to go down all the different 

 shafts and deep workings] ; but in one of the lodes which I saw 

 under ground there was evidently calcite in places associated with 

 the apatite. 



When the apatite of the bunches is associated with limestone, 

 the apatite in part is in crystals, from one inch or less to a foot or 

 more in diameter. The largest crystal that has been got was 

 found in the Emerald mine, just before I visited it, and weighed 

 800 lbs. ; other accessories, such as crystals of black and white 

 mica, amphibole, &c., &c., occur more frequently in the bunches 

 than in the other accumulations of apatite. 



In the Chelsea district (the vale of the G-atineau), nearer 

 Ottawa, where the rocks are not as highly metamorphosed as in 

 the Yale of the Du Lievre (Buckingham township), there are 

 eurites and gabbros associated with limestones and dolomytes ; but 

 I could not find apatite, unless one specimen (which as yet I have 

 not been able to get analysed) should turn out to be it : I suspect, 

 however, it is not so. 



NOTE ADDED IN THE PRESS. 



On examination, the rock iu question was found to contain a small 

 percentage of apatite. 



