152 THE ROYAL SOCIETY OF CANADA 



The marine clay did not suffer any compression in the samples 

 taken, hence in sample No. 3 the total depth of ooze which lies upon 

 it equals approximately ten feet. In all probability this represents 

 the total deposition in this lake since the retreat of the Champlain 

 sea. If the hypothesis that a pair of laminae in the chocolate brown 

 ooze represents a year of time be correct, then the 9h" of compressed 

 sediment of that type ( = 21 feet of uncompressed sediment) repre- 

 sents about 500 years of time only. As nearly as can be judged the 

 other laminae, where they can be differentiated are much thinner, 

 possibly one two-hundredths of an inch (compressed), but even that 

 would represent at a maximum of the thickness of c and d in the 

 section quoted 27|" or about 5,400 years. In most estimates of post- 

 glacial time the period is placed as much higher, from 12,000-15,000 

 years. It is very unfortunate that the laminae cannot be counted. 

 It has been suggested that the slaty-grey clay at the base of the section 

 does not represent the Pleistocene marine clay period, but that it 

 was formed by erosion of the soft marine clays near by, and subsequent 

 deposition in the lake. Thus these beds might be considerably 

 younger than the ordinary marine clays. But no freshwater organic 

 material, which would be the only proof of this, was obtained. In 

 any case only a portion of post-glacial time is here represented. The 

 probability is that the total thickness of freshwater sediment since 

 the lake was formed, exclusive of calcareous material, is present in 

 this section. 



With a view to instituting comparisons in sedimentations, 

 several sections were taken with the Albatross sampler at Fairy Lake, 

 north of Hull. These were taken in a deep part of the lake at a depth 

 of about 60'. Conditions here were quite different from those at 

 McKay Lake. The sediment here consisted largely of heavy stiff 

 clays bluish grey in colour. On examining it with a microscope it 

 was found to be largely inorganic and contained only a small amount 

 of organic material, diatoms, etc. This sediment has been largely 

 derived from the cliffs in the immediate vicinity, and its quantity is 

 much greater than that of any organic deposit. 



The abrupt change from the olive -green zone c and the chocolate 

 brown zone b and the latter and the blackish ooze at the top of the 

 McKay Lake section is worthy of note. It is possible that a change 

 in climate with consequent variation in organic life may have produced 

 this contrast. When the lake was being lowered by rapid erosion of 

 its outlet new conditions arose and if lowered very suddenly as by 

 a flood cutting through the marine clay the same result would occur. 

 A shoaling of fifteen or twenty feet would cause a considerable change 



