•98 Proceedings of the Boyal Physical Society. 



Dr Sterry Hunt stands almost alone in maintaining Serpen- 

 tine to have been at once deposited in its present state. Others 

 hold it as an example of that slow yet sufficient pseudomor- 

 phous action, which attacking the individual constituents of 

 rock masses, has changed arenaceous and argillaceous beds into 

 hornblende, gneiss, or mica schist. The relative position to 

 other beds of the rock we are now specially studying, becomes 

 important. Professors King and Eowney state that their 

 examination of the Lizard Serpentine leads them to believe 

 that it occurs both as a stratified rock and as intrusive masses. 

 They were also able to trace the gradual change from both 

 diorite, dolerite, and hornblende rock into that in question. 



Having had occasion two autumns ago to examine very 

 carefully the Serpentine which constitutes nearly the easterly 

 half of the island of Unst in Shetland, I wish to call attention 

 to its stratified character. This is particularly manifest at 

 the Loch of Cliff, and near the Tree church. At either 

 of these points, as well as at several points on the road 

 from Balta Sound to Uyea Sound, — and this indeed is the 

 western boundary of the Serpentine formation, — a section 

 may be traced on which the Serpentine rests conformably 

 on a bed of black talcose schist, then on limestone, to which 

 again succeed the talcose gneiss and mica schists forming 

 the high western cliffs of this northernmost isle of Britain. 

 Standing in the little land-locked Balta Sound, the tourist is 

 attracted by the varied physiography of the surrounding hills. 

 In front a background of serried gneissose peaks protected 

 in their immediate front by the swelling ground so character- 

 istic of the rapidly weathering Serpentine. Huge boulders 

 with accompanying water pools and great sterility further 

 define this region. I made out the Heogs, Cruci-field, and 

 the peaks of the western side to be dioritic — aphanite in 

 part. Balta Island shows the superior resisting power of the 

 diallage rock to Serpentine. The scenic peculiarities of the 

 Vord Hill, the southern boundary of Balta Sound, are owing, 

 I think, to bands of diallage intersecting the Serpentine. This 

 is the only correction I would make on Dr Hibbert's map. 



I am inclined then (1st) to think the Serpentine beds of 

 Unst and Fetlar a continuous stratified mass ; (2d), the recent 

 microscopic examinations of Drs Rowney and King bespeak 

 a similar scrutiny for this special bed and its congeners. 



