Geology and Mineralogy. 57 
ugi, the able professor of Soleur. The points are these :— 
(1.) The law of long periodicity. — Glaciers vary by long 
| sipeysiae, ten, twenty years or more, not by annual changes. 
he Pfarrbuch of Grindelwald, from 1575 to 1602, underwent 
great elongation; from 1602 to 1620, was stationary; from 1665 
to 1680, shortened ; in 1703, reached its maximum elongation ; in 
1720, reached a maximum retreat, and in 1743, a maximum elon- 
gation; in 1748, again made a maximum retreat; in 1770 to 
1778, lengthened; in 1819, became much elongated, and in 1840 
was still advancing; but from 1855 to 1880, has had a period of 
retreat, 
oes in 1821 by Venetz, and fully propounded in 1831 by F. J. 
a ] - os 
the evaporation of the ice, were struck with the fact of the very 
evident retreat of this great glacier. From observed facts by 
rom 1870 to 1874 the retreat was 71 meters a year; and from 
1874 to 1880 the retreat was 41 meters a year. Thus, through 
24 years, retreat has been going on with no year of advance. So, 
that of the Bossons from 1854 to 1875, and the upper glaciers of 
Grindelwald have continued to retreat since 1855. 
e facts connected with the Rhone sustain the conclusion 
at— 
depends on changes of long periodicity in meteorological condi- 
tions—heat, moisture, winds. 
> 
and these numbers were for the absolute humidity, 14, 10, and 16, 
8; and for precipitation, 14, 10, and 12, 12. Thus the long- 
quently a less long exposure to ablation, and thereby less 
nice; and the reverse for diminished thickness. The gla- 
