The times. [volume] (Richmond, Va.) 1890-1903, 1894-03-18

| ~c,udc air bubbles. But there are aIs'
cher difficulties attending large lenses,
1,hev are greatly affected by expansion anu
i contraction. and when set up on edee
long time they are found to sag. or naSh
together. of their own weight so as 10 III
ference With their correctness. now,
ie,s made I'm sections has none OF these
,oarmI,Ies and IL IL altogether possible
10 make IL 100 rect OF ivo yalu' '''
| ter II desired. - ..o.o-
| Another great advantage Is the cheap
| 80 of construction. More than one
half of the cost OF great telescope ~
| ,resenf Is for the lens. But a lens mace
| a., aactlons is by no means expensive
| There Is reason TO expect that "iinih ="
few, wears any well-to-do man may De
! able to keep "A better instrument INA"
o,-en that at the Northwestern Univer-
/ sitv for the amusement anu s'iuSHo"
/ of himself and family.
! Mr. Gathman claims two or three other
/ discoveries in the construction OF lenses
! which. though not so important as the
! nee Of sections, are interesting when
taken in connection with II. he claims
that the thickness of the sections IS I'M
material. so long as the outer and inner
surfaces preserve the common curve OF
the lens He therefore. would make
the center section one-half the thickness
Of the adjacent sections, only being mind
ful that the surface OF all the sec
lions be described with an equal radius.
The benefit expected from this construc-
ton is lightness. but 1t Is likely that
this construction would not be scientific.
Another project OF Mr.. Gathman is to
reduce the size of the crown glass con-
cavo-convex lens. and place 1t farther
away from the plate glass lens. He sees
no reason why "A forty-inch objective
might not have its crown glass compile
ment so far behind II that il would not
need to be more than six inches in diane
ter. II IL be true that the chromatic co-
servation can be connected at That dis
lance there would. of course, be great
saving OF expense In the manufacture OF
the crown glass lens.
Finally. Mr.. Gathman has been expert
menting In the composition of glass and
is satisfied that II is not only not neces-
sary that the sections Of a lens should all
be composed alike, but desirable that they
should not be. On this point he is Sc
c1etive. The different sections Of his
seven inch objective are made Of several
different krds of glass, and he claims
that this variety destroys tremulousness
in the object Viewed and conduces great
" to clearness and quiet.
But however doubtful these last three
speculations may be. the success Of
lens divided into sections admits OF no
sort Of doubt. The reporter for the TIL
bune has visited Mr.. Gathman's obserVa~
tory and used his telescope frequently.
The objective looks as many-sided as an
cut-glass decanter, and the
objects seen through it are usually bright
and well-denned for an instrument OF
that size. Any one who is skeptical may
90 and see it for himself
one Of the uses to which Mr.. Gathman
has Put his telescope lately is the watch
ing Of the recent phenomena in the sun.
The frequent appearance OF the aurora
borealis. coircidng. as it always does.
with reflections OF the electric needle and
the appearance of spots on the suns sur
face interested Mr.. Gathman, In COM
men with astronomers Of every degree all
over the world, and his observations were
Of more than ordinary interest. lie not
only found TIE spots larger and more nu-
merous. but saw the edge of the photo
spbere notched with them, and saw spots
Of extraordinary brightness as well as
black spots.