Notices of Memoirs—J. Joly—LTolite in Granite. 517 
from Orkney and from the Moray Frith beds, namely, Ch. Trailli, 
Ag., Ch. uragus, Ag., Ch. Cummingiea, Ag., Ch. curtus, McCoy, Ch. 
macrocephalus, McCoy, and Ch. velox, McCoy. Most patient observa- 
tion has however years ago convinced me that there is only one 
species of Cheirolepis as yet known from the British Old Red Sand- 
stone, and that all the differences noted are entirely due to different 
modes of preservation and crushing. A similar view was long ago 
expressed by Mr. Powrie (Grou. Maa. Vol. IV. 1867, pp. 147-152). 
NOTICES OF MEMOTRS. 
J.—Nore on THE ReLarion or THE PERCENTAGE or CarBontc ACID 
IN THE ATMOSPHERE TO THE Lire AND GRowrH oF Piants. By 
Rev. A. Irvine, D.Sc., B.A., F.C.S.! 
HE author refers to the discussion raised recently on this question 
in the pages of the GeoLtogrcan Macazine. In order to test 
the hypothesis adopted by Professor Prestwich, three series of obser- 
vations have been made during the past summer on plants exposed, 
under similar physical conditions, to atmospheres of different com- 
positions. The evidence obtained all points in one direction, and 
goes to show that, with an increase of the percentage of carbonic 
acid up to about that of the free oxygen present, the vigour of plant 
life and growth is also increased, so long as the plants are freely 
supplied at their roots with water, as we have good reason to suppose 
was the case with the vascular cryptogams from which the carbo- 
nized materials of the Coal-measures are for the most part derived. 
The author further considers the theory as throwing some light upon 
a certain stage of development of life upon the earth in later Palzo- 
zoic time ; the great development of plant growth in the Carboniferous 
age having served as the means of storage of carbon in the earth’s 
lithosphere, and thus purified the atmosphere so as to render it fit 
for the development of air-breathing forms of life in the Mesozoic age. 
I].—On THE Occurrence or JoLiTE IN THE GRANITE OF CoUNTY 
Dusuy. By J. Jory, M.A., B.E.t 
OLITEH, not previously noticed in Irish granite, has been found 
by the author in the granite of Glencullen. It occurs as a 
microscopical but abundant inclusion in a substance of felspathic 
nature which is to be found interpenetrating prisms of beryl. Its 
presence is confined, apparently, to the felspar so intermixed with 
beryl. The iolite is in twelve-sided basal prisms, showing the faces 
I, i-l, i-3, i-l, O. In size up to 0-1 mm. in length, transparent, 
colourless viewed singly, and presents a vivid and beautiful object 
in the polarizing microscope. Characteristic features are the basal 
angles of 150°, 120° or 60°; its generally symmetrical extinction on 
elongated rectangular sections and the transverse cleavage on such 
sections. A foliation or plating on O, and an oblique twinning-line 
parallel to J, are also frequently met with. Occasionally the crystals 
occur in radiating groups. Inclosures are rare, generally glass. 
1 Read before Section C, British Association, Bath, September, 1888. 
