Reports & Proceedings—Geological Society of Glasgow. 285 
imparting to it a characteristic lamprophyric appearance; vesicles 
with secondary minerals appear towards the margins. 
In thin section, idiomorphic biotite, olivine pseudomorphs, and 
felspars are seen to make up the bulk of the rock; chlorite and 
secondary quartz occupy the interstices. 
Analysis yields a small percentage of alkalies, the potash being 
slightly lower than the soda. - 
One of the thin sections was seen to contain crystals of blue 
corundum associated with magnetite, in a patch which was obviously 
foreign to the rock. With the object of obtaining additional 
examples, many slices were cut, sections being made of those that 
seemed promising. In this way several of these inclusions were 
obtained, the largest being about 0°3inch in diameter. All contain’ 
corundum and magnetite, but in some cases staurolite also is present 
and more rarely green spinel. Further information concerning the 
corundum and staurolite was obtained by crushing the rock, and 
separating the constituents by means of heavy liquids. A well-formed 
crystal of the former mineral is tabular, large basal planes being 
combined with a subordinate rhombohedron, and it is probable that 
all the corundum of the rock is tabular in habit. 
The corundum, staurolite, green spinel, and associated minerals 
probably owe their origin to a process of inclusion of fragments of 
the argillaceous country rock, and very definite borders of biotite 
surrounding some of the inclusions suggest that these are merely 
unassimilated remnants of larger fragments. 
Il.—Gerotogicat Society ofr Giascow. 
1. At a meeting of the Geological Society of Glasgow on April 13 
Mr. Alex. McLean read ‘‘ Notes on the Age of the Human Race based 
on Evidence found in Post-Pliocene Strata”. He referred to the 
_opinion held in certain quarters that the age of the human race was 
not many times greater than the sum of the classical and historical 
periods, and quoted many authorities to show that, so far from this 
being the case, the investigations carried out during the last half- 
century had produced evidence of a vastly greater antiquity. In the 
ancient river gravels and in caves and on other sites human relics had 
been found which gave clear evidence of a series of well-marked 
stages in the progress of the race from a state of extreme simplicity. 
Mr. H. R. J. Conacher read ‘‘ Notes on an Occurrence of Petrified 
Plant Remains in Lower Limestone Strata at Bridge of Weir”. He 
said that in the strata immediately underlying the Blackhall Lime- 
stone in the banks of the Gryfe there was exposed a group of about 
half a dozen tree-stumps. These showed the well-known external 
characters of the roots of ZLepidodendron and Sigillaria, and in 
addition parts of the internal woody tissue. The main axis showed 
that a kind of ‘tap-root’ had existed, and a series of slowly tapering 
ironstone cylinders, with calcite cores, which penetrate the embedding 
shale, no doubt represent the rootlets proceeding from the spreading 
roots. So far none of these rootlets have been found with any 
vestiges of internal structure preserved, but such may yet come to 
