GEOLOGICAL T^TOTES IN" THE GREAT EXIIIBITIOV. 



389 



The proximity of the sorpontine leaves no doul)t as to their <rcolo^jfical 

 horizon being that of tlie Quebec, grou]) of tlie Lower Silurian. Four 

 other samples of slates have been sent to the Exhiljition ; of these, the 

 Cleveland and the Shipton slates are a continuation of the Melbourne 

 band ; the slates from Orford may be of the same band ; but the geological 

 horizon of those from Tring is uncertain, although tlicy p)-(jbably belong to 

 the Quebec group. The Kingsey slates ai)pcar to be lower in the series 

 than the magnesian group of strata. Flagstones are exhibited from the 

 Medina " grey band," and hydraulic lime from the Clinton formation at 

 St. Catherine's. The bed which yields this — " the Thorold cement " — is 

 a dark brown dolomite, and 80,000 bushels have been annually made. 

 There is another sample of hydraulic lime from Walkerton, made from 

 beds of 2 to 11 miles, occasionally separated by layers of shale, in the 

 total amounting to 15 feet, and belonging to the Onondaga formation. 

 The jU'actical manufacture of this latter cement has not however been yet 

 attem))ted for commercial purposes. Other samples are also samples 

 from Limehouse (Clinton group), Nepean (Chazy formation), E,ockwood 

 (Niagara grou])), and Magdalen Iliver (Hudson lliver formation). Com- 

 mon lime is shown from stone belonging to the Guelph and Onondaga 

 formations, and from the building-stone of Montreal, where 270,000 tons 

 are annually made. 



The connnon bricks exhibited are all made from drift or alluvial clays. 

 Whetstones are shown from the Quebec group, Hudson Eiver, and Medina 

 formations. The mica-slates also which are associated with the crystalline 

 limestone of the Laurentian series arc frequently of the character required 

 for scythe-stones. The whetstone rock occurs in immediate contact with 

 a thick band of conglomerate, the pebbles of which are frequently large, 

 some of them 6 inches in diameter ; they are chiefly of quartz, but some 

 are of feldspar and some calcareous. The quartz pebbles are for the most 

 part distinctly rounded. Some of the siliceous slates of the Huronian 

 series yield very fine hones ; they are usually of a green colour, and 

 occupy a place in the lower part of the series. Grindstones are shown 

 from the Medina "grey band," and millstones from the Oriskany forma- 

 tion. Millstones or dressed buhrstone (Laurentian) is also exhibited from 

 Grenville. This buhrstone constitutes a series of veins cutting an intru- 

 sive mass of syenite, which occupies an area of 36 square miles, amongst 

 the Laurentian rocks of Grenville, Chatham, and Wentworth. The veins 

 consist of yellowisll-bro^^■n or flesh-red cellular chert, and the stone lias 

 the chemical composition of flint or chalcedony. The attitude and asso- 

 ciations of the chert show clearly that it cannot be of sedimentary origin, 

 and its composition taken in conjunction with the igneous character of the 

 district suggests the idea that it is an aqueous deposit which has tilled up 

 fissures in the syenite, and is similar in its origin to the agate or chalce- 

 dony which in smaller masses are common in various rocks. For a distance 

 of perhaps 200 yards on each side of these veins of chert, while the quartz 

 of the syenite remains unchanged, the feldspar has been more or less 

 decom})Osed, and is converted into a sort of kaolin. As this process 

 involves a separation of the silica from the feldspar, it is not improbable 

 that it has been the origin of the veins of silex. 



Mineral manures are now an iin])ortant division of economic geology. 

 Gy])suin is shown from the Onondaga formation on the Grand Eiver ; al- 

 luvial freshwater shell-marl from (leposit-i at New Edinburgh. Monlr(>al. 

 and many other })laces ; and calearecnis marl is shown from Noisy Kivi-r 

 falls, where it covers the extensive slopes on both sides of the river, ))ro- 

 bably covering an area of 300 acres in the vicinity of the falls, \\ilh an 



