t>8 EXPEDITION TO THE 



terruptecl in numberless places by veins of coarse-grained 

 granite. In some cases we see in these veins apparently 

 fragments of other rocks imbedded in them. These frag- 

 ments, however, are always composed of one or more of 

 the four simple minerals which constitute the whole mass, 

 viz. quartz, mica, feldspar, and amphibole. Although they 

 present the appearance of fragments, still we see no reason 

 to doubt their being of contemporaneous origin ; indeed, 

 when examined with the microscope, we have frequently 

 traced a gradual passage of the feldspar of the vein into 

 that of the imbedded fragment ; it was not a mere impreg- 

 nation of the rock by the feldspar, as is often observable 

 in the vicinity of metallic veins, where the rock has re- 

 ceived a portion of the metal of the vein ; but we could 

 trace an uninterrupted union in the crystallization of the 

 feldspar of the vein with that of the imbedded mass. In 

 some cases also, veins posterior in formation to the mass 

 of the rock were distinctly observed. They were fre- 

 quently seen intersecting older ones in a gneiss rock, and 

 exhibiting very beautiful and diversified instances of a 

 shift or slide of the older vein at its intersection by the 

 more recent one. 



In the afternoon, we passed in the river several rapids 

 and falls, which occasion what are called by the voyagers 

 the " Decharges" and the " Portages." The former term 

 is applied whenever the obstruction is but a partial one, in 

 which case the canoe is lightened, and either paddled or 

 towed over the rapid. In such cases the passengers always 

 leave the canoe, and as much of the baggage or load is 

 taken out as the shallowness of the water requires. The 

 portages are those places where the obstruction being 

 greater, the whole of the cargo, as well as the canoe itself, 

 has to be carried over ; these vaiy much in length. We 



