744 



SCIENCE. 



[Vol. II., No. 44. 



maps, that xtuxy well serve as a visitor's guide. 

 Primitive old-fasliioned ways have endured on 

 these remote islands till recent times, and fur- 

 nish manj- anecdotes to enliven the descrip- 

 tive pages. The more scientific student, with 

 a liking for botany', geolog}', mineralogy, or 

 archeologj-, will meet with much worthj- of his 

 attention. 



The two geological chapters, prepared b}' 

 Messrs. Peach and Home from their papers 

 published in the Quarterly journal of the geo- 

 logical societj' and elsewhere, are of chief sci- 

 entific value, and are well illustrated by neatly 

 colored maps. The southern group is shown 



siderable variety of old raetamorpliic rocks, and 

 numerous intrusives and eruptives. The rela- 

 tions of the latter to the adjoining masses is 

 often finelj' exposed in the sea cliffs, and (lues- 

 tions of age are not left to vague inference. 

 Dikes, necks, intrusive sheets, and overflows 

 are all well exhibited. But the geological inter- 

 est culminates in the glacial question. These 

 northern islands give the key to the movement 

 of the combined Norwegian and .Scolcli ice- 

 sheets, and show, as was first suggested by 

 Croll, that they joined forces in the basin of 

 the North Sea, and together moved north-west- 

 ward, out into the Atlantic. The striae are of 



HEAD AND THE OLD MAN OF HOY UURIJ 



to be almost entirel}' covered by the various di- 

 visions of the old red sandstone ; and, indeed, 

 this formation once extended over a great area 

 thereabouts, now broken up into ragged islands 

 by dislocation, erosion, and submergence, so 

 that only the smaller part of the original depos- 

 it remains. The topographic effect of former 

 erosion at a higher level, followed hy depres- 

 sion, is seen in the irregular shore-line and 

 fringe of islands shown in the view of Scal- 

 lowaj'. In their present attitude, the islands 

 suffer most along their western coast, where 

 the heavy waves of the Atlantic cut them back 

 into imposing clifTs, such as are found on the 

 western side of H03'. Shetland includes a con- 



two dates. The later ones depend on the local 

 topography for their direction, and are referred 

 to a 'later glaciation,' though it is not shown 

 that a non-glacial interval separated this 

 from the greater or primary glaciation, during 

 which the ice moved independenth* of local 

 topograph^', over-riding all the hills and ridges. 

 Onlj' these are shown on the accompanying 

 outline, which is traced and reduced from 

 two maps of much larger scale in tlie original. 

 On the Orkneys the scratches run north- 

 west with much regularitj'. ISIarine shells 

 and rocks derived from eastern Scotland are 

 found in the bowlder-clay. On Shetland the 

 approach of the ice was from the north-east, 



