34 E. Petitot on the Athabasca District 



measurement and bulk, and of elegant or grotesque shapes, from 

 buttons and turnips to the planet Saturn with its rings. 



I have never seen in any geological text-book an explanation of 

 the formation of these lenticular concretions, geodes, or pisolites, 

 which I cannot believe to be merely concretions of sandstone rolled 

 and rounded by the action of water. I am inclined to the opinion 

 that they are masses thrown up in a globular form by some sub- 

 terranean igneous force, and falling into the water holding much 

 mud in solution, in which they have passed from a pasty condition 

 to a solid consistency, crystallising as it were in it by the action 

 of cold. I adopt this view, because these pisolites (whether 

 geodes or not) are only met with in this district near rapids and 

 waterfalls, in localities exhibiting numerous traces of subterranean 

 fires, formerly much more active and powerful than now ; and 

 because I have found some of these concretions composed of iron 

 pyrites, crystallising from the centre outwards, and also others 

 of bog iron. Whatever may be the method of formation of such 

 singular freaks of nature, the Athabasca in eroding a tortuous and 

 deep channel through the sandstone of Bark Mountain, finds its 

 bed obstructed by these gigantic concretions, which are the sole 

 cause of its rapids, and render its navigation so perilous as to be 

 well-nigh impossible. Besides this danger, great numbers of them 

 are exposed on the sandy surface at all heights of the cliffs, form- 

 ing immense caps constantly threatening the heads of the unsus- 

 pecting travellers beneath. 



Remarkable vegetable fossils are often found in the sandstone of 

 this part of the Athabasca, imbedded in the rock, but capable of 

 detachment with the hammer. I have noticed whole trunks of 

 Cupressoxylon (probably a Sequoia), characteristic of the ter- 

 tiaries, and have sent specimens of it to Montreal and to Paris. 



Near the Clear-water a pudding-stone begins to appear in 

 horizontal layers from the level of the water, probably also reach- 

 ing below it. This conglomerate is here overlaid by oblique 

 stratifications of bituminous schist, which transude asphalt from 

 top to bottom. The savannas and swamps covering the surface 

 of these rocks conceal rich mines of bitumen under their thin 

 coat of turf; and from Point Colbert to the Pierre-a-Calumets 

 river they have given rise to the Chipewyan name of " Ellel 

 DesseY' or " Kiver of the moving grounds." 



