The Bamberg herald. [volume] (Bamberg, S.C.) 1891-1972, 1904-12-15

mechanical occupat tions. The resi-
dence is that Of Max Kahler. famous
among scientific men, who employ op-
tical Instruments as an adept i'll the
. difficult art of lens making. Mr.: Kali
Ter has made some OF the most delicate
lenses in use at the Naval ODserya-
tory, the Astrophysical Observatory OF
the Smithsonian Institution, and other
scientific establishments throughout
the country. while 4 number Of fine MI
croscopes, together witt, I large pro-
portion of thcodolites employed by sur
veyors. owe their excellence TO the
lenses which he has turned ont in his
simple little workshi1.
A person does not necessarily have
to lie versed in scientific matters TO re-
alize that the accuracy Of the images
transmitted by such instruments as
the telescope, camera. microscope, ETC..
depends entirely upon the perfection OF
the glass surface upon which the i'm
age is received and through which it
is conveyed to the human eye or the
sensitive plate. We are all acquainted
with the wayy looking glass. which
may be purchased for few cents, and
which represents the human face di-
rine' most fearfuliy and wonderfully
distorted. Between such glass as
this and one that would faithfully re-
fleet all object with nearly absolute
exactness, there is, as far as regards
mere cost, difference Of several hun
dred dollars.
But the value to the scientist cannot
Le over estimated of an exact plane or
curved surface Of glass. The former,
especially, principally required in mir
rors for receiving the suns image. is.
as Mr.. Kahler will explain, one of the
incest achievements in the making Oh
optical instruments. In illustration OF
this fact, Mr.. Kahler pointed to a disk
of glass, sixteen inches in diameter,
which was conspicuous upon a dusty
work bench. This was to be made in
to a mirror for one of the instruments
of the astrophysical observatory of the
Smithtonian Institution, and the work
which was to be done upon it, and
which would occupy some six weeks
of persistent labor of the most skllfui
and laborious description. was to put
O perfectly smooth or plane surface
upon it. When this was accomplished
the unpretentious piece of glass would
be worth $1,000. This may appear
strange to a person accustomed to re-
gard the French plate looking glass in
his room as having perfectly plane
surface and rejecting his image with
absolute exactness. To all practical
intents and purposes, indeed, the latter
object is accomplished; nevertheless,
the surface of the glass is long way
from being a plane in the scientific
meaning Of the word, and in the re-
auirements of optical instruments.
In order to realize the value of these
accurate mirrors, one has only to ex-
anime the method employed for taking
a photograph of the sun each day at
the Naval Observatory. The image
of the luminary is first received upon
a mirror and thence transmitted to the
mouth of the camera. These sun pho
tographs disclose, with the most ex-
quisite minuteness, the structural fea-
lures of the suns s'envelope," as the
luminous mass surrounding it. has
been termed. The so-called sun spots,
for the observation of which these pho
tosraphs are principally taken, are
shown in wonderful detail, the peeu-
liar fibrous structure attributed TO )ets
of flame and the different densities
being clearly distinguishable. 1t is
scarcely necessary to observe that II
the mirror transmitting the image IN
the first place, were not a perfect
plane, or something very near it, the
picture, depending for its value upon
such minute detail, would be distorted,
confused, and absolutely worthless Tor
scientific purposes.
"How do you test the surface of the
glass in order to ascertain whether. or
not it is perfect plane:,' MI. NaIter
was asked. y
For answer, the worker in optics took
two pieces Of plate glass. These 1
use merely to Illustrate" he explained.
"Of course, these are by no means
plane surfaces, though they are about
as much so as will be found in the or
dinary fire mirrors Of commerce. l
use a plain surface for the purpose OF
actual testing, which place over the
surface I am working on just as
place this piece of glass over the
other. Then take q piece of metal
screen and dip it in salt mixed with
some infammable liquid. and so get the
yellow sodium rays. Now. after plAc-
ing this simple apparatus in the TIL
pod here, I hold the two pieces OF
glass so as to catch the sodium rays,
and YOU will notice the innumeraole
lines, black and white alternately, that
traverse the surfaces of the glass III
all directions. These lines, in accu-
4 ,,,,,os would no ab0ut half an