THE LAURENTIAN AND HURONIAN PERIODS. 75 



traces of life have been detected, which may subsequently 

 prove of great interest and importance. Thus, Principal 

 Dawson has recently described under the name of Archceo- 

 sphccrince certain singular rounded bodies which he has dis- 

 covered in the Laurentian limestones, and which he believes 

 to be casts of the shells of Foraminifera possibly somewhat 

 allied to the existing Globigerincs. The same eminent palaeon- 

 tologist has also described undoubted worm -burrows from 

 rocks probably of Laurentian age. Further and more extend- 

 ed researches, we may reasonably hope, will probably bring 

 to light other actual remains of organisms in these ancient 

 deposits. 



THE HURONIAN PERIOD. 



The so-called Huronian Rocks, like the Laurentian, have 

 their typical development in Canada, and derive their name 

 from the fact that they occupy an extensive area on the borders 

 of Lake Huron. They are wholly metamorphic, and consist 

 principally of altered sandstones or quartzites, siliceous, fels- 

 pathic, or talcose slates, conglomerates, and limestones. They 

 are largely developed on the north shore of Lake Superior, 

 and give rise to a broken and hilly country, very like that 

 occupied by the Laurentians, with an abundance of timber, 

 but rarely with sufficient soil of good quality for agricultural 

 purposes. They are, however, largely intersected by mineral 

 veins, containing silver, gold, and other metals, and they will 

 ultimately doubtless yield a rich harvest to the miner. The 

 Huronian Rocks have been identified, with greater or less 

 certainty, in other parts of North America, and also in the 

 Old World. 



The total thickness of the Huronian Rocks in Canada is 

 estimated as being not less than 18,000 feet, but there is con- 

 siderable doubt as to their precise geological position. In 

 their typical area they rest unconformably on the edges of 

 strata of Lower Laurentian age ; but they have never been seen 

 in direct contact with the Upper Laurentian, and their exact 

 relations to this series are therefore doubtful. It is thus open 

 to question whether the Huronian Rocks constitute a distinct 

 formation, to be intercalated in point of time between the 

 Laurentian and the Cambrian groups ; or whether, rather, they 

 should not be considered as the metamorphosed representa- 

 tives of the Lower Cambrian Rocks of other regions. 



As regards the fossils of the Huronian Rocks, little can be 

 said. Some of the specimens of Eozobn Canadcnsevi\\\c\\ have 



