, 1877-07-23
Tho f1reAt lick Te}cscopS.
Gan Ekdntihca HuIIkffu

Richard &. F1oy., one OF tho Trustees Of Tho
Lick Trust tlas Just returned from MI cTteu!cd
European tour. During his ns'scnrc lie has
cr countries, hut almost Invariably found them
afralu to commit Themselves to nj, ordni'm ~ TO
whether a greater success cas1 he obtained With
ruaccting or 5efractlng telescope: rsol. N.Y.
his visit to Europe to look Into this ltlastcr for
Mr.. Lick, reported s'arfn1y III favor of KRsn-
tic refsnctoE, and furNnrlcd complete csttMRes
as 10 the cost. [te has since chaugch hts orl1'-
iun, however, and now tccanmcnds a .,tycr-on-
glass reflector Ut nbont seven feet dtatnf ter.
Ross's, llcrsehcl's and other celebrated tc!c-
scopes have apcculnm-mela u rLlcttors, w!cl.
the palm Is clnimed Tor an ,uscntdoa, Il Leon
F0urault'e by which silver tl1 solution IL Ie-
posted on glass. Foucauit made rctlector upon
this system about thirts.onc and 1ste-h!t' Inches
in diameter. anA excellent work has hcen
accomplished with It. After his death rctlce-
tnr upon this plan about four fcta In III an,cter
was constructed for tho observatory. o!;!ng to
sumo not thoroughly explained utse this has
not proved success, an4 another Ut the saine
Dimensions Is being constructed ~ repl arc y.
Grcat Interest Is manifested in the usut Of this
second experiment, Which ca1lnot be prtnfcn Tor
rear yet. Dr. nuegns. tic %e'lkno. sn q at, !.
better for srcctrosroptc ana1ysls, bis 1svoEla0
study. 1t is natural tlat be should ,arcfer re-
ac,t.,r as te tcstscA to hayo the field OF physical
astronomy enlarged.
Theoretically reflector Of four feet, tn diainc-
ter is about equal to = rcfractor Of twcnty'slr
lncilcs The ftoss reflector Is six feet IN diam.
ctcr, ony four feet Of which are eft rtive, and
So lar II has not been proven that moro t!ian
four feet OF reflector cnu bc made effective.
The great trouble With the reflector IL that 4 Is
very sensitive to atmnsnhetic chanefs. while
with tic rctracter the difficulty lies i,x Tho scc-
! ontlary spectrum. Tho objcct.Elass Of the re-
| tractor IL composed Ut two glasses Joined, tho
outcr being Of crown glass, tho inner OF flint.
! Rays passing through the crown Elues arc re-
| frartcd, md entering the flint glass urc re-
| rcfracaed. Tho consequence Ii that perfect
a4!,romatism Is impossible, and tho difficulty q
aornycnsatlnR these Tcfracttons increases With
tho ktxc OF tho object glass. Inc lArtcst rctras-
] tor In tho world Is that In the Washington OBJ
scrvatofy; It is twenty-siK Inches In diameter,
! anl is nj excellent fhttrtlinent.
Mr.. FLOYD saII that nftcr u careful an EXAM
| ination as be could make, ho II inclined to be
| leyc that tho hest inttreoth Of tho :uua will he
| served, to laYo constructed II latRs:r rcfractor
| than any yet mule. This ought not to cost,
| complete, fnnrc than Sl5u,010. Then there will
! be subsidiary reflector, about four icct fD d.
ameter, supplied with both stver'oTrElass and
| saccuum metal mirrors. sslch an instrument
has been offered. or rather parties httyc ncrcct,
| 10 construct one, for shout 90, ,0o0, Tell. Of
| Paris, will undertake tn make crown anu Hint
plass uiscs for tho object glass OF forty.inchfc-
Traitor for SO 00O0stlpulatlng that 10 shall be
allowed two ycnrs for their coltstructh,n. After
they have left his haAda tho ort'eian will require
about thruo yeafs more to figure thcsU dIscs
uathematfral1y.