214 FIFTEENTH LETTER ON GLACIERS. [1848. 



Mr. Milward was not aware that the analogous phenomenon 

 was discovered by me in glaciers as far back as 1843, and 

 A 



|Fig. 24. SECTION OF GLACIER DU GEANT. 



described in my Fifth Letter on Glaciers,* where I have 

 given the preceding plan and section representing them. It 

 must be as satisfactory to Mr. Milward as it is pleasing to 

 me, to find that his shrewd conjectures as to the probability 

 of their discovery, although based solely on the analogy of 

 viscous fluids, are thus perfectly confirmed. They were, in 

 fact, discovered in the place and at the time that Mr. Milward 

 supposed they would be, and they were already designated 

 by the very term he uses, " wrinkles," years before he wrote 

 of them. " It will be useless," he observes, " to look for 

 them at the lower parts of glaciers, as they will have disappeared 

 under the effects of atmospheric and other action. . . It is, 

 therefore, to the head of the glacier, where the true glacial 

 structure commences, that we are to look for such ridges : the 

 best time, also, will be at the commencement of summer, after 

 the disappearance of the snow, and before the confusion of the 

 surface occasioned by the sun's influence." t In point of fact, it 

 will be found, from the reference above, that the glacier wrinkles 

 were observed on the Glacier du Geant, at the upper part of the 



* Edinburgh New Philosophical Journal, 1844, p. 117, and pages 40 and 41 

 of the present volume, where these figures occur. 



f [An Attempt to illustrate the Origin of "Dirt-bands in Glaciers." By A. Milward, 

 Esq. Edinburgh New PhilosophicalJournal, Jan. 1849. The remarkable insight into 

 phenomena which this paper displays, and its intimate connection with the subject 

 of the present Letter, induces me to print Mr. Milward's contribution as an Appen- 

 dix to the present volume ; the rather as it might easily be overlooked in the volu- 

 minous journal in which it first appeared. The account of the Mud-Slide at Malta 

 (which is not reprinted) is also well worthy of being read. The writer of these con- 

 tributions to the theory of Glaciers is now unfortunately deceased. He died about 

 two years ago in the neighbourhood of Clifton, where I had first the advantage of 

 making his acquaintance in 1852. His very bad health must have prevented him, 

 for a great many years from exploring a glacier, if indeed he ever had that advantage. 

 His deductions are therefore, in every respect, the more remarkable. Dec. 1858.] 



