It is composed of felspar, quartz and mica, takes 

 a brilliant polish, is extremely hard and lastio^, 

 and is most useful for a variety of purposes. Al- 

 though so bard and lasting^. it cannot stand for 

 ever. When flood and torrent have removed all 

 later deposits from the granite rock, the slow, but 

 very sure and certain action of the rain, charged 

 with carbonic acid from the atmosphere and 

 humus acids from the soil, eats the life out of the 

 solid granite rock, decomposes it, washes it 

 in the form of mud to lower levels ; there 

 it settles and we call it " kaolin" and it is from 

 decomposed granite that we get our china cUys, 

 our earthenware, and our brickearth. For build- 

 ing purposes, to stand the test of ages, Cleopatra's 

 Needle, The Temple ot the Sphinx, the marvellous 

 granite Panes in the Island of Philae, are pointed 

 to as the one lasting material ; but ne )ook at the 

 wonderful clay cylinders and tablets from Babylon 

 and Asfcyria, and learn that probably the most 

 lasting material upon this earth is the well- 

 burned brick, made of clay largely com- 

 posed of this decomposed granite. The sil- 

 vered plate-glass mirror is perhaps a compara- 

 tively new dtivice, and before its introduction, 

 ladies were glad to use highly polished metal for 

 the purpose, but in very early times the material, 

 called " obsidian," was probably the only mirror 

 available for our predecessors. It is of volcanic 

 origin, a black and glassy kind of slag. The well- 

 known pumice is the same materirt.1, but frothed 

 up into a t'pungy, cellular formation by steam or 

 gas, and floatd on water. Basalt is another 

 volcanic lava, generally black, always compact, 

 heavy, too bard to tool for building purposes, but 

 used largely for road making; it breaks with con- 

 choidal fracture. This rock often assumes a 

 columnar form, as shown in the lale of Staffa and 

 Fingal's Cavtf. Perhaps the pretty rock known 

 as Lnbiadoiite is the general favourite among all 

 the igbbuus rocks. It is composed of 50 per cent. 

 ftl(*par and 50 per cent, silica, and when polished 

 is largely Ubed tor shop fronts, drinking fountains, 

 monumt-ntti, etc. 



Metamorphic. — We now pass upwards to the 

 rocko wtiOoo natures have undergone a complete 

 change, which must have taken ages to complete. 

 These ate tot med " Metumorphiu" (simply meaning 

 change of form). It does not require any great 

 Btreich of the imagination to see that the black 

 igneous rocks when reduced to powder through 

 various agencies, should be washed into cavities 

 in the btato of black mu'l ; such is the origin of the 

 rootiug blate so abundant in Wales, and although 

 nothiug but clay, is so consolidated by intense 

 pressure, tnat when split up, is most useful for 

 many purposes. It does not t^plit along the sur- 

 face of deposit, but through what is called " cleav- 

 agw" pret-oure, splits at right antjle^. Gneiss is 

 to all lutentsand purposes a granite, but tnrough 

 the process of sbeanuu, has become a fine grained 

 and crystalliae mass ; it looks very much like gran- 

 ite, and ltd composition is the same. In some 

 sases it is foliated granite. Through the grinding 

 up of the oldf t silicious rocks, a v^ist quantity of 

 fine silicious sand would be cirried by the elements 

 and deposited, perhaps, in the se i, there to undergo 

 consolidation into quartzite — that hard, compact, 



granular rock of a light and lustrous appearance, 

 so useful for road-making and so plentiful at Cher- 

 bourg. Perhaps of all the stones that could be 

 laid before you, marble would be the m'^st gener- 

 ally known and appreciated. It is a calcite rock,, 

 and must have been formed in very early times by 

 chemical precipitation or organic agency in commoa 

 with all limestones. Its present crystalline charac- 

 ter is due to both heat and pressure. When pure,, 

 it islalways quite white, statuary marble command- 

 ing the highest price ; its infinite variety in colour 

 and marking, is simply due to impurities. 



Laurentian. — We now pass upward to what are 

 termed ." Neptunic " rocks. The lowest strati- 

 fied rocks are caled " Laurentian," because they 

 show themselves so well in the mountains along 

 the St. Lawrence in Canada. They aie vast and 

 venerable sediments of primaeval seas, highly 

 metamorphic. Heat, moisture, and pressure have 

 changed their sandstones into sparkling crystallise 

 rocks, and their limestones into veined and varie- 

 gated serpentines. They were formerly classed as 

 "Azoic," that is without life, but certain struc- 

 tures lately found in them are pronounced by some 

 authorities to be the remiins of a large foramani- 

 fora, which has been named " Eozoon Canadense." 

 Possibly the best known rock from this system 

 would be the "Graphite," previous^ly referred to as 

 carbon; it is an amorphous greasy feeling mineral 

 of dark steel colour, and with a metallic lustre. 

 It is always found in these primary rocks, and in 

 many parts of the world. The best quality, used 

 for lead pencil?, was found at Borrowdale in Cum- 

 berland, but in 1875 the mine was nearly worked 

 out. It was of such value in 1803, when the mine 

 produced 500 barrels, each IJ cwt.,that it fetched 

 303. alb., and as a cartload wuuld be wort.h over 

 .£;5,000, it was sent under military escort from the 

 mine to Kendal. At such a price it. is not difficult 

 to understand why pencils cost 6i. each, but in 

 the days of "imitation " and '• substitu'e," when 

 pencils can be bought for 2^ ^.a■^^•z-n and upwards, 

 the explanation is that an artificial preparati in is 

 made by dissolving charcoal in molten iron, which, 

 on cooling, gives out some of thfiCirbonin the form 

 of graphite. The Laurentian system has a vast 

 thickness of oyer 30,000ft. — or six miles. 



Cambrian. — Next in order is thw " Cambrian " 

 system. When you travel in W^les you notice 

 the rolling stock, etc., is called " Cambrian " 

 R'lilways — Cambrian being the ancient name of 

 Wales — the rocks in this system being particularly 

 visible in Wales. The typical "ocic is sUte ; our 

 chief supply is from Wains — Bangor— Penrhyn, 

 and Port Madoc being particul-irly engaged in 

 splitting their rocks into roofing slate. At this, 

 period the earth had auflScently cooled on the 

 surface to permit of life. There is a d -ubt about 

 the E 'Z )on Canadense, but no doubt whatever 

 about the remains and markings of » kind of sea- 

 wt^ed and of the small peculiar crustacean ciUed 

 '* graphtolite," so called becau-e of tneir resem- 

 blance to qmll pens. In sum" pUc-s the slate is 

 full of these remains. The ('ambra'i sy-tjm has 

 a proved thickness of over 20,000 feet, and is 

 lichly vMined with metal ores. 



Silurian — We now arrive at th» " Silurian '' 

 system. la the Border district of Eagiaad and 



