332 Notice of a Scientific Expedition. 



entirely exposed, b is another part which is partially concealed by 

 a layer of limestone shelving over it. It is evident, therefore, that 

 this dyke has been brought to light by the wearing away of the up- 

 per layers of limestone. The circumstances accompanying this 



Fiff. 1. 



dyke suggest the thought that it was projected into the limestone 

 while it was yet forming, and in comparatively a soft state ; and that 

 that portion of the limestone which shelves over the dyke, and other 

 portions which have been worn away, were deposited after the dyke 

 was driven through the rock. If so, then we have a clue to the com- 

 parative age of the greenstone. Whatever theory we may have on' 

 these points, it is plain that dykes may sometimes exist when they 

 do not appear at the surface. 



The last mineral locality visited by us in the neighborhood of 

 Lubec was the lead mine. It is about eleven miles from that place, 

 and is owned by Mr. Thayer. The immediate gangue is much like 

 that at the Southampton lead mine. The ore is the common sul- 

 phuret accompanied by the sulphuret of zinc. There are three 

 vertical veins in the neighborhood of each other. Their width va- 

 ries from one inch or two to a foot, and in some places they bulge out 

 to three or four feet. Judging from appearances, we should infer 

 an abundance of lead, but the gangue is a very tough variety of 

 quartz ; the expense of working the mine is so great that it is quite 

 unprofitable at the present price of lead. We were disappointed in 

 not finding any of the salts of lead at either of the veins, though we 

 have been informed that the sulphate and carbonate have been pro- 

 cured here. 



Returning from a visit to the mines just before sunsetting, we 

 were gratified with the sight of a fine athiospheric phenomenon. 

 The day had been very foggy much to our discomfiture. But at 

 this time the atmosphere began to clear up. The fog seemed to 

 gather into strata of different densities, with surfaces as distinct and 



