Clinch Valley news. [volume] (Jeffersonville, Va.) 18??-2019, 1897-04-23
FACTS FROM An oLo NAP.


Remarkable showing of repograph-
&c Changes I'm Two Centuries.
IL is well known that our Appalachian
mountains were once very much higher
than the Rocky mountains OF to-day;
and that the reason why they are now
comparatively low mountains is simply
that they are very old and have been
worn down by denudation. The same
destructive influences are still degrad-
ing them, very slowly as we measure
ordinary time. to ,lower levels. We
know that changes are constantly go
Ing on in the physical condition of the
earth's crust. but these changes are SO
slowly accomplished that they eau
scarcely be observed, i'm many cases, in
IAN ordinary lifetime. In the coming
ages students of physiography will have
q great advantage over those Of to-day;
for the art of accurately delineating the
surface of the earth by means OF con-
toured maps is comparatively recent
invention. Hundreds of years from now
the Photographers will be able TO
learn from the maps we are making
now exactly what the surface features
of large areas were in our time, and ID
will be easy to make instructive com
PARSONS with the same features as they
find them.
Prof. Edunrd Bruckner has recently
described i'm Petermann's Mitteilungen
the very interesting results of a COM
parative study of u remarkable map OF
the seventeenth century and one of the
Swiss survey maps OF to-day. In 1867
Mr.. j. G.. Gyger completed his map Of u
part OF the Alpine region extending
from the lshino on the north to the
Reuss on the south, and including the
whole of the canton of Zurich, in Switz-
erland. The map was on an unusually
large scale for that time. The scale was
]: 32 900, or one inch on the map for
about half mile in nature. He worked
compass in hand, paced his distances,
and was very careful and laborious in
his survey. He gave 4 great deal of
time for 81 years to his map. He was the
first TO use lights and shadows to indi-
cate and contrast mountain slopes. Two
copies of his map, both signed by him,
are eXtant, and they still excite the adj
miration of photographers for the won
derful accuracy with which they de
pict topography. Until this century
the Gyger map was regarded as tho
best photographic delineation of the
Zurich canton. Small parts of il have
been published with corresponding sec
lions of the present surveys, to show
the high standard of accuracy Mr.. CIV
ger attained.
Mr.. III. Walser has carried out, in the
geographical institute of the University
OF Berne, the comparison between the
Gyger map and that of the present day.
MIR. Cyger carefully showed every lake,
large and small, in the canton and sharp
~ distinguished the lakes from svyamps.
His map showed $40 likes in the canton.
or these no less than % arc not found
on the present maps. These lakes, as
Mr.. Walser points out, one by one, have
become extinct. They were all small, !
most of them having an area of less than
2J acres. The area of 10 other lakes is !
now much reduced, and 20 others are
somewhat smaller than in the seven
teenth century. Forty lakes have un-
dergone no important change.
Mr.. Walser has ascertained by obser. !
vation the causes of the shrinlxage or
disappearance of 81 of these lakes. The |
farmers, in their efforts TO secure more |
meadow land, have played an Important
role. They have drained quite n mum. |
Ler of the lakes and turned their beds !
into hay farms or pasture lands. OIL
course. in geological time. all lakes arc
drained by the natural cutting down OF !
their outlets, but, on account of the /
rnimportant slope Of the outlet chan |
nels of these particular lakes. the deep /
ening of the channels was very slow
and this form of lake effacement seems |
to have cut no figure.
The effects of two other natural
causes, however, arc very evident. One !
was the sitting up of the lakes by the
deposit OF sediment, and the other, and /!
more important, the gradual cncroach /
nent of plant life in the lakes, which |
finally completely filed them, the de |
cay of vegetation forming soil and thus |
the lakes were gradually eXtiDguishetl. |
Some of the lakes are still undergoing |
this process, the carpet of plants ex. ]
tending all around the shores. while (
n little water surface is still visible in /
the center. The deposition of sediment !
and the growth of plants which finally !
obliterated these little lakes were, of
course, supplemented, as Mr. Walser |
says, by the human activities that, in I
the past century. largely cut off the !
water supply that made and fed them
N. Y. Sun.