SECRETARY'S REPORT. 179 



Greenland. You pass from a New England to a Greenland 

 climate, in these mountains, in an hour's walk — owing merely 

 to tl^e difference in height. Now, this is the condition under 

 which the snows which accumulate in the higher regions may, 

 passing down to a lower level, be transformed into ice ; and the 

 motion of this whole mass will vary according to the amount 

 of moisture which results from the partial thawing, and to the 

 progressing of the freezing and the moisture. Now, without 

 entering into details, let me at once put down some of the 

 results. At the height where the process of thawing is very 

 slow, the motion in a year may be ten or twenty feet. Lower 

 "down, at an elevation say of nine thousand feet, it may be forty 

 or fifty feet. At seven or eight thousand feet, it may be as 

 much as one hundred and fifty or two hundred feet. Where 

 the level is about six thousand feet, we have a movement which 

 may be two hundred and fifty or three hundred feet a year. 

 Now comes a singular change. Further down, the motion 

 becomes less and less. And why ? The ice is compact. It 

 is so compact that there is no thawing within, but there is 

 melting on the surface. There is a slight moisture penetrating 

 into this mass, and in consequence of this, a little expansion, 

 so that in proportion as the ice begins to be so compact that it 

 can no longer receive water in its interior, and expand by the 

 freezing of the water, the motion is reduced ; so much reduced, 

 that at the lower end, the movement may be only sixty or 

 seventy feet a year. When it started at the snow fields in the 

 higher regions, it had an initial movement of ten or twenty 

 feet ; it increased to two or three hundred feet, and was finally 

 reduced to a movement of seventy feet, on slopes which are the 

 same, or which do not present any great difference in steep- 

 ness — showing distinctly that this motion is not determined by 

 the slope, but by meteorological influences ; that is, by climatic 

 influences, — by the amount of moisture, and by the frequency 

 of thawing and freezing. 



Now, these differences of climate you may have, on a level, 

 in different latitudes ; and a glacier, or mass of ice, or sheet of 

 ice, may move on a level quite as much as down hill, if on one 

 side of the mass there is frequent thawing and freezing, and on 

 the other side only a continued accumulation of snow ; and I 

 have satisfied myself, by a process which would be too long 



