Evening star., 1898-09-10
AN AMERICAN "BLUE GRoTTo.v
A Beautiful Cavern Located Beside
Lake Minnewaska.
From Science.

FROM Science.
Many of The beautiful phenomena seen
at the celebrated Blue Grotto of the Island
OF Capri are reproduced on a small scale
in cavern at Lake Minnewaska. New
York. This lake is situated on the Shaw
ansunk range of mountains, at an eleva-
ton of about 100 feet; it lies in a basin,
excavated in glacial times, about half q
mile long and less than a quarter in width,
and Of depth reaching seventy feet
The rock on all sides is a white quartzite
known as Shawargunk grit, which rests
upon shale, but no outcrop of the latter
Is visible at the lake The quartZite IS
compact to granular. and contains in plac as
pebbles Of white quartz; it is very free
from feldspathic admixture So that it
yleiuS TO the water very little soluble mat
ter. Bare cliffs rising to the height OF 1.n
feet bound the east side of the lake While
the western hanns are well wooded The
cliffs are vertical AID fringed a: thpir base
by the usual talus, vi ich, howev-r. is made
up of blocks of unusual size.
The cavern is formed by ee~efal hn-o
rocks overhanging the water so as TO form
mparatively dark hole. AMI III sl.:tcc
between the under side of th4 slipping rocks
and the water varies from -,oOuI two feet
to not more than two inches. In. cavern
faces the southwest; it is very ire gll1 ir
in shape and at one point tha ,.oof and
walls reverberate in response TO a deep
bdSS mote ne Nsl'fr 'uSt "a lIn entrance.
of the cavern is thjrty-three feet deep. ara
TWO or three Feet aFay forty feet: it is
very transparent al considerable depths
AS the rocks ovarhang 8" close 20 the
water, the optical cffac.s can only be seen
by swimmer. and I was while swimmin :
along the shore mat | discovered the Amer
lean blue grotto inree wears ago As ore
approaches the mouth f thS cavern the
blush color of he water Is roriceablr hut
the beautiful effects are best seen by on
tering the opening and .oakin., outward
toward the light. 'rna water varies in o.
or from Nile green through turqu )ise blne
and sky blue TO deep indigo blue, and in all
these shades exhibits the silvery appear
ance, when agftated, characteristic of the
grottG at Capri. A body immersed in the
water has beautiful siivery sheen. similar
TO the reflection of moonlight The water
has these colors at all hours. but they are
strongest when the sun is in the zenith:
late in the afternoon the Slanting rays of
the sun enter the opening and light up the
fects.
The water retains the characteristic color
Cbut without the silvery sheenD on cloudy
days and even during rain. being especial
ly strong when fieecy white clouds bar
direct sunlight. The relation between the
different hues green ana blue to the as
pect OF the sky, whether clear or over
cast is not evident.
Another pleasing phenomenon must be
mentioned. just below the water line,
where tie rocky sides are lappcd by the
waves, the white quartzite exhibits bril-
liant stslln-green hue; this bright color is
limited TO space about three or four
inches below the level of the lake and TO
certain walls of the cavern. The bare arm
immersed In the water partakeS of the
green color when the light is reflected at
one angle. and of the silvery blue color at
another angle. The interior size of the
cavern Is not easily given, but the face of
the overhanging rocks measures about
forty feet and they project about fifteen to
fC ,es,
small a cavern can produce such a variety
of fine effects.