10 



A difficulty at the oneet presents itseU in dealing 

 ■with the fragment of a large subject to select 

 points for illustration and interest, so I introduce 

 it to your notice as it was presented forty-eight 

 years ago to mine at Stirling Castle. 



Unfortunately, for picturesque effect and scien- 

 tific inv^stigation, the i ail way runs on the wrong 

 aide, so that thousands must pass by without 

 being aware of the beauty ami interest to be found 

 on taking what is locally known as the Back Walk. 

 a footpath running along the west and north side 

 of this Castle, which is certainly founded on a 

 rock, and that lock once in a state of igneous 

 fusion. The carse of Stirling h^s it= levnl surface 

 penetrated by thiee such rocks within about a 

 mile of each other, and in a line running from west 

 to cast — Craig Forth, Stirling Craig, and the 

 Abbey Craig, on which now stands the Wallace 

 memorial. 



Stirling Craig might weil be taken asa volcanic 

 core, but on ploser inspection these craigs will be 

 found to be intorbedded traps tilted more or less 

 on end, having their perpendicular fronts facing 

 the we&t. The hollow under the talus of Stirling 

 Castle is strikingly suarj^estive of wave action 

 when tides flowed througli the valley now occupied 

 by tlie carse of Stilling. Whether it be a break- 

 water or a sea-cliff, the storm wavt'S striking a 

 perpendicular object rise to a great height and 

 then falling down again, scour out the base of the 

 <.bstructioD. forming a trench or hollow, running 

 parallel to its front. In wet weather I have seen 

 water filling the ditch-like hollow running under 

 the western side of the Castle rock. 



The dip of the interbedded traps, and wave 

 action will account for the long slope to the east 

 and precipitous western faces of these craigs. 

 In theeaily morning I have seen from the Castle 

 walls the valley filled with white cloud, but the 

 three craigs rearing their rocky faces above the 

 white billows of mist, like islands in the rock 

 bound inland seas of the west coast. 



A very remarkable feature of these rock« is their 

 prismatic character. Passing along the Back 



Walk in a noitherly direction, and looking up 

 about 150 feet above the path, this becemes more 

 and more pronounced, until it culminates at the 

 northern face in a group of columns, one of which 

 has fallen over, and, leiting upon its neighbour, 

 forms a natural bridge. 



The shores of the Clyde and the Island of Arran 

 are seamed with trap dykes, but perhaps one of 

 the most remarkaVilH monuments to volcanic 

 energy and denudation is afforded by the Island 

 of Eigg, where an ancient river arorge of a vanished 

 land has been filled to overflowing by a lava 

 stream, now forming a wall of basaltic columns 

 twelve hundred feet in height. 



Among the most remarkable examples of tne 

 fissure flow of lava are the marvellous trap dykes 

 that cleave Ben Vorlich, 2,950 feet in height. 

 Loch Lomond. 600 feet in depth, passing through 

 ttie noithern exten=;ion of Ben Lomond 2,0<X) feet, 

 and running for seven miles plunge throueh the 

 waters of Loch Katrine. The extraordinary 

 denudation that has excavated valleys 3,0<X) feet 

 deep, and dug lochs 600 feet deep out of their 

 rocky beds since this welling up of molten lava, 

 has given to the face of nature those features that 

 are indicative of their parentage — volcanic action 

 and denudation. 



The beauties of Oban, the marvels of Skye, 

 Staffa,and the Giant's Causeway, show the extent 

 of the earth's surface affected by volcanic action, 

 an area calculated by Sir Archibald Geikie at not 

 less than one hundred thuusand fqnare miles 

 having a thickness ia the Island of Mull of thiee 

 thousand feet. 



As we occasionally come across the stump of 

 some grand dd forest tree, so must wt- regard 

 what is now left, as but tlie i uots of the mountains 

 that once reared their peaks in Alpint- grandeur. 



Linking our geology of Kent with this volcanic 

 district is the outlier of the chalk, preserved under 

 a sheet ot lava that forms the Giant's Causeway, 

 which by chemical action induced by heat and 

 pressure has been transformed intoasubcrystaline 

 iimestjne resembling white marble. 



SIXTH WINTER MEETING.— JANUARY 2oth, 1903. 



'COLOUK PHOTOCtR.\PHY."— By Mr. PRANK MIALL. 



The sixth winter meeting uas held in the Beaney 

 Institute on January 20, wnen iVlr. Frank Miall, 

 of Luniieie Ltd., gave a very intererfliuij demon- 

 stration of trolour pho'ogr^phy by the Luuiiere 

 process. The whole of the lecture was very 



attentively followed, and the speaker proved how 

 simple a matter it had now become to take true 

 photogr.iphs of Nature in all their beautiful and 

 varied hues by means of the above process. 



