(Correspondence. 275 
deposit, spread over hundreds of miles of a broken topography and 
reaching- a thickness of a hundred feet, could not very well be as uni- 
form in its mechanical composition as the loess is. It would more fre- 
quently contain coarser mateiials. In particular it seems improbable 
that a water deposit, as fire as the loess, should be without thin seams 
of fine silt, such as are generally to be observed in aqueous sediments. 
These are more or less conspicuously laminated. In a (fine) wind sedi- 
ment on the other hand such a sorting and lamination is impossible, 
owing to the smallness of each sorted load, to the less constancy of the 
depositing current, and to disturbing agencies which are at woi-k thor- 
oughly mingling successive deposits on the surface of the land." 
I appreciate the difficulties attending the reporting of all the papers 
presented at such a meeting, especially when the reporter merely hears 
the papers read once and has no opportunity himself to see the manu- 
scripts. The above correction is cheerfully made. 
Respectfully, J. A. Udden. 
Hock Island, III, Sept. nth, 1891. 
Toronto Meeting of the British Association for the Advance- 
ment OF Science. The presidential address of Dr. G. M. Dawson to the 
section of geology dealt with the recent jirogress in our knowledge of 
the crystalline rocks of Canada. He referred to the establishment of 
the doctrine that the greater part of the Huronian beds were of volcan- 
ic origin. In his view the Laurentian fundamental gneiss existed orig- 
inally as the floor on which the Huronian was deposited. The Gren- 
ville series has been shown by analysis to consist of the same material 
in ultimate composition as the Paleozoic argillites and is probably meta- 
morphic, while the anorthosite group is found to consist essentially of 
intrusive rock, often folded, later in date than the Grenville series, but 
probably pre-Paleozoic. 
The same structure prevails in New Brunswick and there the funda- 
mental gneiss is in contact with a series of limestones, quartzites, and 
gneissic rocks, precisely like those of the Grenville series. All these are 
unconformable beneath fossiliferous beds, regarded by Matthew as old- 
er than Cambrian. The same is true of the Cordilleran region. 
The speaker then passed on to the consideration of the base of the 
Cambrian system and the range of the term ''Paleozoic." The former 
is at present arbitrary and paleontological, and the latter is now extend- 
ed by some to include all fossiliferous strata downward. 
In both these respects he expressed doubts regarding the possibility 
of maintaining this practice as the field grew wider. '"On the Atlantic 
side the Olenellus zone is a fairly well marked base for the Cambrian; 
on that of the Pacific it is found naturally to succeed a great consecu- 
tive and conformable series of sediment whose more ancient fauna is 
only now beginning to be known." 
Dr. H. M. Ami discussed the little known formations and faunas of 
Ordovician age in New Brunswick and Nova Scotia and after attempt- 
ing the subdision of these formations by their faunas, he essayed their 
paralellism with their taxonomic equivalents in Europe. The Devonian 
and Carboniferous systems were treated in like manner. 
