464 SCIENTIFIC RECORD FOR 1888. 



tively barren ; all of which facts would seem to favor the hypothesis 

 that the supply of the precious metals in the lode has been dissolved 

 from the diabase. The present writer, twenty- five years since, called at- 

 tention to the dissemination of small quantities of ores of copper and 

 of nickel in the greenstones of the Huronian series, and also to the fact 

 that, while the quartz lodes carrying copper (and sometimes nickel ores) 

 pass from the greenstones into the adjacent quartzites, they become bar- 

 ren; a fact which was regarded as evidence that these veins were filled 

 by lateral secretion. 



