ANNIVEKSARY ADDRESS OP THE PRESIDENT. IxV 



organic structures ; for whilst large quantities of them are found at 

 each of the localities of Grenville and Calumet, in masses which are 

 entirely destitute of remains of Eozoon, and yet would seem to have 

 been deposited at the same time, other portions appear to have had the 

 organic structure obliteratedby cleavage-planes due to the crystalliza- 

 tion of the pyroxene. In the accompanying strata, we are informed, 

 finely crystallized pyroxene, hornblende, phlogopite, apatite, and other 

 minerals often occur, " These observations," says Dr. Hunt, 

 " bring the formation of siliceous minerals face to face with life, and 

 show that their generation was not incompatible with the contem- 

 poraneous existence and the preservation of organic forms." More- 

 over they support a view previously put forward by him, that 

 " these silicated minerals have been formed, not by subsequent me- 

 tamorphism in deeply buried sediments, but by reactions going on 

 at the earth's surface." And in support of this position he has 

 reminded us that, in recent as well as ancient deposits, the most 

 dehcate forms of organic structure have been in some instances pre- 

 served by the infiltration of the mineral glauconite, so well known as 

 the colouring-substance of the Greensand, and itself a hydrous com- 

 bination of silica with sesqioxide and protoxide of iron, with alumina, 

 and potash. Supposing that in the ooze at the bottom of the sea 

 dissolved silica comes into contact with iron- oxide rendered soluble 

 by organic matter, the resulting silicate deposits itself in the cavi- 

 ties of shells and other vacant spaces. " A process," Dr. Hunt 

 suggests, " analogous to this, in its results, has filled the chambers 

 and canals of the Laurentian Foraminifera with other silicates; 

 but, from the comparative rarity of impurities in the silicates, it 

 would appear that they were deposited in clear water"*. 



Since Wohler (above twenty years ago) showed how apophylhte 

 could, as a laboratory experiment, be dissolved in water, and be 

 reproduced from the solution in crystals, abundant proofs have 

 been given of the power of water, especially at an elevated tem- 

 perature and if saturated with carbonic acid, to destroy many 

 silicate minerals, and also, under varied conditions, to recom- 

 pose a number of familiar species, particularly among the 

 hydrated sihcates. Even the extreme feebleness of the action 

 which carbonic- acid water, and water under great pressure f, exer- 

 cises upon many of these minerals, and most notably on silicates of 

 magnesia, must not be allowed to blind us to the numerous examj)les 

 which prove the efiicacy of this agent. Such are : — the green- earth, 

 lining the interior of amygdaloidal cavities ; neolite, a hydrous 

 silicate of magnesia, which is formed at the present day in one of the 

 iron-mines of Arendal ; and meerschaum, occasionally exhibiting the 

 form of Helix and several freshwater shells in the marl-beds of 



*■ Quart. Journ. G-eol. Soc. 1864, p. 71. These observations and opinions have 

 been restated, in connexion with additional matter on the Eozoon, in the ' Report 

 of the G-eological Survey of Canada' for 1866, of which the proofs have kindly 

 been forwarded to me by Sir William Logan. 



See also the excellent paper on Glauconite, 'by Haushofer, in Jour, fiir prak. 

 Chem. 1866, p. 361. 



t Bischof, Chem. Geol. vol. i. pp. 3 and 31. 

 VOL. xxiii. e 



