Plate xviii.  Residues of denudation.  The Matterhorn seen from the
summit of the ZINAL ROTHHORN — to face p. 148

Plate xix.  The folded rocks of the Matterhorn, seen from near
HOeHBALM.  Sketch made in 1906 — to face p. 156

Plate xx.  Schiaparelli’s map of Mars of 1882, and additions (in
Red) of 1892 — to face p. 166

Plate XXI.  Globe of Mars showing path of in-falling satellite — to face p. 188

Plate XXII.  Canals mapped by Lowell compared with canals formed
by in-falling satellites — to face p. 192

Plate XXIII.  Haloes in mica; Co.  Carlow.  Halo in biotite
contained in granite — to face p. 224

Plate XXIV.  Radium halo, much enlarged. Thorium halo and radium
halo in mica — to face p. 228

Plate XXV.  Halo round capillary in glass tube.  Haloes round
tubular passages in mica — to face p. 230

Plate xxvi.  Aletsch glacier, Switzerland — to face p. 282

Plate XXVII.  The middle Aletsch glacier joining the great Aletsch
glacier.  Glaciers of the LAUTERBRUNNEN Thal — to face p. 285

Plate XXVIII.  Perched block on the Aletsch glacier.  Granite erratic near roundwood, Co.  Wicklow; now broken up and removed — to face p. 286

And Fifteen Illustrations in the Text.

x

PREFACE

Tins volume contains twelve essays written at various times during recent years.  Many of them are studies contributed to Scientific Reviews or delivered as popular lectures.  Some are expositions of views the scientific basis of which may be regarded as established.  Others—­the greater number—­may be described as attempting the solution of problems which cannot be approached by direct observation.