Dealing with the great peaks the geologist is at no small disadvantage as compared with the surveyor, whose instruments enable him to work from a distance and to fix with accuracy the position and height of the object of his observation. The geologist, on the other hand, must toil arduously up the mountain sides, examining at close quarters such outcrops of rocks as he can find clear of snow, and, where further progress is barred, must depend for his information on fallen fragments, splintered from the cliffs above and brought down by avalanches and glaciers to form moraines and talus heaps.