86 M. Renoir on the Traces of Ancient Glaciers^ 



tain when made between the polished surfaces of these coun- 

 tries and those which, in the southern parts of Europe, so 

 clearly indicate the ancient existence of glaciers. M. Robert 

 says,* " I traversed all the southern coast of Finland, from 

 Helsingfors as far as Abo, passing across the innumerable 

 small islands scattered along it. All of them, without excep- 

 tion, have been evidently covered by the sea 2ivA perfectly po- 

 lished, as well as the rocks on the coast, emn to a great dis- 

 tance into the interior of the country ^ We here repeat, that 

 in our opinion this perfect polish is the work of masses of ice 

 moving immediately over the surface of the rocks, in the same 

 manner as the presently existing remains of glaciers have po- 

 lished the rocks over which they move, and are daily continu- 

 ing to do so. What confirms us in this opinion is, that there 

 are numerous furrows, to use M. Robert's words, sometimes so 

 distinctly marked that they can be perceived at some distance, 

 especially when the surface of the rock is wet. In regard to 

 the glaciers of the Alps, we often see on the rocks which they 

 have long since left, entire surfaces covered with fine striae, 

 which may, in like manner, be seen at some distance, even 

 when the rocks are dry. If, then, the furrows of the polished 

 rocks of Finland are striae, it appears to us that there can be 

 no doubt that its surface was formerly covered with ice. These 

 furrows, besides, are all parallel ; for M. Baer affirms that he 

 never met with a single example of a furrow crossing another. 

 In addition to this, it appears from M. Robertas report, that 

 they all run in the general direction of the valleys, and cross 

 all the strata indiscriminately without regard either to their 

 direction or hardness ; for, after having stated that these fur- 

 rows are generally parallel to the laminae of the gneiss rocks, 

 M. Robert adds (in the same page) '* In short, it is worthy of 

 remark that the veins of quartz or of other substances usually 

 cross the direction of the erosions at an angle more or less ap- 

 proaching to a right angle, and never run in a parallel direc- 

 tion with them, as takes place in lamellated rocks." All these 

 circumstances taken together, prove that these furrows have 

 been tracedby hard bodies moving in concert at fixed distances, 

 that is to say, attached to the same solid body which prevented 

 them yielding to any obstacles they might encounter. 



- "-* Fulletin de la Society G^ologique de France; t. xi. p. 328. 



