PEESIDBNTIAL ADDEESS. 7 



"But it remaius to be considered," says the author I have already qvioted, " whether 

 there is equally strong warrant for considering this series to be structurally and conse- 

 quently chronologically separable from the adjoining portions of the so-called Archaean. 

 Is it not possible that we are merely setting off arbitrarily a set of rocks, which is really 

 only part and parcel of the whole great Archaean complex, and is not separable by any 

 genuine line of demarcation ? " I agree with Prof. Irving that we are setting off what is 

 really part of the Archaean, but I think the general distinctness of the Huronian is 

 sufficient to justify the division, and that the difference between the two sets of rocks — 

 Huronian and Laurentian — is great enough and easy enough of recognition to justify the 

 separation. Why do we draw lines anywhere in the geological scale ? Is it not for the 

 convenience of description and the classification of our facts, in order that we may the 

 better fix our ideas ? Our present systems among the higher rocks might have been 

 made more comprehensive ; and Murchison, for example, wished to make his Silurian 

 System include nearly the whole of the Palaeozoic rocks. Nothing would be gained by 

 including the Laurentian and Huronian under one system. On the contrary, there is 

 great convenience and utility in retaining these appropriate and well-established divisions ; 

 but it will be difficult, on general principles, to justify a further division of the Huronian 

 as it has hitherto been recognised by the Canadian Survey. "While the Huronian, as thus 

 defined, forms a natural division which can be easily separated from the Laurentian, it is 

 impossible to practically draw the line between the crystalline schists and the quartzite 

 portions, even if it were desirable to do so, which it is not. "Why should we, therefore, 

 seek to establish a division which it is admitted cannot be defined either on a geological 

 map or by description. If we look at a geological map showing the known Htironian 

 belts or areas all over the continent, we shall see that they occupy everywhere the same 

 place in regard to the Laurentian, and that it is manifestly vinjustifiable in the present 

 state of our knowledge to pick out any one or a part of any one of them and call it a natural 

 geological division, recognisable as distinct from all the rest. Although the Huronian 

 rocks are conformable to the Laurentian, as a whole, and might, therefore, be regarded as 

 a continuation of the latter, still, as already remarked, their general character is so different 

 and so easily distinguished that they constitute a sufficiently well defined set, and the 

 more we know about them, the more useful and natural does this separation appear. The 

 lines between other systems of rocks are not always drawn at great physical breaks, and 

 why should we insist on one here before recognising the Huronian as entitled to rank as 

 a system ? On the other hand, a local discordance between two of its members, or the 

 fact that some of the higher ones contain fragments of some of the lower, would not con- 

 stitute a sufficient reason to place these different members in separate geological divisions 

 of important rank in the scale of classification. The upper members of any series are apt 

 to contain fragments of the lower, and this sometimes within comparatively narrow limits, 

 such as those included under the term " formation." 



In his descriptions of the Huronian, Prof. Irving does not give sufficient prominence 

 to the igneous nature of a large proportion of the system, but, as already stated, rather 

 conveys the impression that its great feature is its iron-bearing character. The second 

 part of this author's paper, under the above title, begins with the declaration that 

 " deciding that the type Huronian is a true group, is a difierent matter from concluding 

 that all rocks which have been called Huronian in other regions are the geological equi- 



