218 TRANSACTIONS. 
to elucidate the matter as was deserving of it. Until this could be 
done we might and would go on floundering in the mire. This 
was one of the cases in which by judiciously interfermg with the 
balance of nature a vast amount of profit might accrue to the pos- 
sessors of our fisheries. It was like a valuable mine of wealth 
unworked. 
7th of March, 1890. 
Major BowDEN in the Chair. 
New Member.—Mr Robert Maxwell Witham of Kirkconnel. 
Donations.—Transactions of the Edinburgh Botanical Society ; 
Annual Report of the Belfast Field Club; Report of the Berwick- 
shire Naturalists’ Club ; Bulletin on the English Sparrow in North 
America and North American Fauna, from the United States 
Board of Agriculture. The Transcription of Edgar’s History of 
Dumfries from the Riddell MS. was also handed in. 
COMMUNICATIONS. 
I. Zhe Succession of Plant Life upon the Earth. By Mr 
PETER GRAY. 
After a brief exposition of the nature and mode of deposition 
of the sedimentary rock strata in which the remains of previously 
existing plants and animals are found, the author enumerated 
their principal sub-divisions and defined the four life periods in 
which they have been further arranged, namely, the Azoic (with- 
out life), the Paleozoic (ancient life), the Mesozoic (middle life), 
and the Kainozoic (new life). There were nu dates in the 
geological record, and, as to the length of time occupied in the 
laying down of the sedimentary rocks, there was the widest 
diversity of opinion. Physicists, judging from the rate of cooling 
of the globe, and other data, were unwilling to place the time 
when it was possible for plants to exist upon it much farther back 
than from ten to fifteen millions of years. On the other hand, 
some geologists asked for at least six hundred millions. Of the 
shortest of these periods, however, we could no more form a 
competent conception than we could of eternity. Proceeding then 
to a detailed examination of the sedimentary deposits, from the 
earliest upwards, the author stated that though no fossils had 
been discovered in those of the Azoic period, yet the immense 
quantity of carbon, in the form of graphite or plumbago, occurring 
