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XXXV . On the Motion of Glaciers. 

 By E. H. Koch and Fk. Klogke*. 



THE measurements hitherto made upon glacier-motion 

 have either been only approximative determinations of 

 the annual or daily mean velocity, or have been executed for the 

 purpose of showing that the motion of glaciers corresponds 

 with that of liquids ; while investigations upon the actual 

 course of this downward motion are wanting — whether, namely, 

 it proceeds 'continuously in the same direction, or whether it 

 is discontinuous, stoppages or even reversals of the motion 

 taking place. From the observations made by M. PfafF on 

 the nevef the latter is probable even for the motion of glaciers. 



Our investigations were limited to the observation of a point 

 of the surface in a vertical plane parallel to the longitudinal 

 direction of the glacier ; the measuring of the lateral motion, 

 and the motion of the deeper layers of the glacier, as well as 

 observations during the night, were for the time excluded. 

 Nevertheless, from the facts which have up to the present time 

 been observed, it can already be concluded that the motion of 

 a glacier is not at all uniform ; for one and the same point may 

 now move toward the mountain, now toward the valley, now 

 ascend, now descend. It was further found that two points 

 of the surface, distant from 50 to 60 metres from one another, 

 can move in different, nay, in opposite directions. 



The method chosen for the observations was that employed 

 by M. Pfaff, and already used for other purposes. Two scales, 

 one perpendicular to the other, were fixed upon the glacier so 

 that the one was vertical and the other horizontal ; their move- 

 ments were observed on the cross-threads of a firmly placed 

 telescope. The number of scale-divisions travelled over by the 

 cross-threads gave then directly the horizontal and vertical 

 components of the motionj. 



The examinations were made in the days from the 28th of 

 August to the 6th of September, on the west side of the Mor- 

 teratsch glacier. The observing-station was about 1\ kilo- 

 metre distant from the lower principal extremity of the glacier. 

 This situation was selected on account of the firm ground 



* Translated from a separate impression, communicated by the authors, 

 from Wiedemann's Annalen, 1879, vol. viii. pp. 661-666. 



f Abh. d. math.-phys. Classeder h. bayer. Akademie derWissensdiaften, 

 xii. Abth. 2, p. 105 seqq. 1876. 



\ The telescopes and tripod stands were kindly intrusted to us by the 

 Director of the Freiburg Mathematical Cabinet, Prof. Lindemann, and by 

 the Director of the Physical Institute, Prof. Warburg. 



