New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1868-11-26

science after the invention OF re balance OF iaon 81
So"pc electricity is under obligations equally great TO
The Ingenious Instrument called the galyanometer. PIN
era atirg eonometcr The brilliant advances OF the
present century IN physical optics have been sded III
cal analysis has found In the specroscopo an admraDe
auxiliary the decacy OF It's ACKNOWLEDGEMENTS "a, aux
,iiory which has already brought 10 light four new
netSls of which the existence had not been previously
susnected and which busyng itself successfully WIN
and t6e nebun the field OF Physiology and sir9ctu
raj Anatomy is the microscope when mas 5no
arst rank among tho instrumental aids TO lnVesglo
and which may almost be said TO nave created ,no
which It illustrates III proportion as II mas 'tSe
viii now endeavor to explain in brief manner rs
nosslbe and with the help OF illustrative di'gtais t
ronsrcton OF this beautiful instrument, ana the primer
ples on which ts usefulness depends; ,., ,oa ,ror,
THE name microscope defines Itself III Is loIusa iy I
aa words signfying 20 observe the minute, as tele
scone signifies TO discern the distant microscopes nav
pe9 veil IA npon those of refracton 1t the re-
fractinp microscope which is III common use ~
stand ts construction It necessary 10 reeI 20 so @
starv nroperties OF light medium IN optics IS any
space through which light can pass whether u 90 sTI VI
occupied by matter In solid, nuid or gaseous o
30 ~ Sht passnc from medium TO an0ther per
pendicnlarly the bounding surface MAINTAIN ter
lion unchanged. II Inclined to THIS SURFACE tney nv
NANCE their direction, refracted As rule the
raw will be to the perpendicular III tng aeso' t
dunn than in the rarer The angie OF incdeneS IL teao
made by the incident ray with The t
angle Of redcon that made ny the IeIGaeSu iy tbet
the same perpendicular. The tdio OF rgTaW.t 's sa az
tho sine Of the gle OF incidence divided by the SIRE OF
the angle Of refrsotion. gives lnyaIlaDy ne ste
This Qitoiienf or ratio, "a called the ae1 g
Parallel rays transmitted at any incnatloh thIomsn
by parallel faces continue 10 nc parallel
DivergiDg convergng rays under snliar Gi.ou ~
stapees become more dycrgng or less coLNeIRlbg ~
radiant they longer have this character aer uahs
mission but said TO DO affected by Goeirdu0h Inns
eeS en used TO observe objects covered many are
with thin glass plates and requires special eontryoe
faces inclined to each other viii be nnequally Teractea
by the different faces and may be made felayey 10 az
verge or to converge after transmission IL Is eyluSnt
mai the faces may be so multiplied and so adjusted to
each other make AL the transmitted rays ntetsect
must he ipinito in number, or the surface must be
cttrrA IL - not difficult To determine mathemaucay
An eIllpso will do it, Elliptic curves are not, however,
used i'm the construction OF the microscope.
tics 10 concentrate scatter rays OF light Only spher
cal curvatures gwen TO lenses. Some
overcome and IL possesses advantage on the OtneF
hand which belong 20 no other Ihe points on lhSIseo
zion Of couyergcut rays called fOc Inc locus OF par
sel rays is the principal focus The term radiant is APP
piled 10 focus nom which rays dlyerge Rays rom
radiant more distant than the principal focus OF con
vex lens will 20 second focus on me oteT s1e
Of the lens, Tho two are called coJugate oC. Lays
from point nearer 10 the lens than its prncpal FOCUS
viii emerge divergent but less divergent than Dtlorcas
II they proceeded from more datant rauian,' tis
more distant radiant IA called the imaginary or negative
iges ano ~ I.l the caefs are All the OF those
Win cono9N1 - s.ed - n sinrie radiant au object
| OF sensible guitude be placed before convex
an independent radiant, having ts corresponding colJu
cate foens and these conugato foc will combine TO pro-
s sD aee OF the object which win be Inverted and
reyersed m the object. be nearer than the principal
icons "a ali the emergent rays will be divergent no real
image viii be formed but there Will be negative or
imaginary Image the same side OF the lens as inc oD
sc II tho eye Of an observer be placed PENN inc es
hooking toward tho object. this Imaginary image VIII ap
pear be real. and will be The thipg seen spherea
lenses do not produce trno foci henco the images
by single lenses imperfect When parallel rays arc
Transmitted through convex lens the focus OF the cen
tra rays Is more distant than that Of the marginal IN
ternedate rays form foci AZ intermediate distances Inc
erai foc are distributed Is called tue spetedi liberation
of the lens II Aliens - unequay curved on us Two sues
or me other side presented 20 PARALLEL rays Generally
speaking parallel should DO received on ho s4uo
| having the largest curative.
Tho alteration OF concavo lenses r. the OF that
Of convex a concave lens. combined win convex OF
H. fornhtion such concave lens in the position Of
maximum abefrati d, combined With convex ~ tho
position O.. minimum alteration viii hentfai2e n9ella-
r,ou irey, and produce perfect focus. tbs u tue
principe which the 1rst Of tho grave dlmeucs 10 me
would loo In lenses formed OF substances more highly
reacins th5 sacS lenses would he tRaner t6sn glass
lenses Of equivalent power and alteration Is IA definite
iimes The thickness with the hat slide toward parallel
rave and only oncsxth Of the thickness With IA" e"eas
gems the difficulty ~ grinding them the color OF some
o. them, and tho property Of , NV ,
they are Proposed TO remedy hofo'sf S' 1sH no S
needed. But there another aDeIrA'Ioh no no
los troublesome than tho spherical WmcI,,
~ elementary rays differing from each other very sehsi
b., In tfrau giuiiy. aud alto in color lie familiar eN
sr are tho red AMI the violet; but the violet Il very
flint We may regard FOR our present purposes the red
and the blue as representing tie limits. Ihr blue rays
exceeding the red in Tcianpbiiy VIII FORM ~ image
nearer the lens than the red And between thcS I'M
total number OF images thus formed Is uhhittd' ana
spion Color win be- Visible only the margin Of tho
| blended images ChromRtio alteration "a tho second
great difficulty DC overcome In the construction OF the
croscope il happens fortunately that the separation
OF the coios technically called dsperson) ny different
media IA not proportional 10 the rofractng power As
te dsperous OF and concayo lenses are IN oppO
site directions combination OF two such lenses may DC
obtained IN which dispersion snh 20 WINE
there stu remains balance Qf Tefraetng power out
standng Thus concave lens OF mint glass VIII correct
the dispersion OF more powerfully refrneung convex
len. OF crown glass; and the image formed by the com
| blnation will be cooress. IL IS then mathematical
eston 10 ind the curyaures proper To be gwen 10 such
lenses to correct spherical and conatc aDerra
| ton at the same time.
third great difficulty TO be contended with in tho CON
srncton OF this Instrument results from the fact that
the image OF plane Obect formed by any single lens Is
not plane, but curved Hat object observed through
an eyeglass TO round up toward the eye In the
center positive image Of such an object, formed by
convex lens, Is followed out, or concaye toward the
lens Moreover though the spherical alteration may be
corrected for the axis Of the lens VIII not be so for the
obque rays. Distortion OF the form OF the object OBJ
served and confusion IN the marginal portions OF the
image will therefore stu remain, even after the correc
Ons above described have been made 10 conquer this
last difficulty, 30 AS TO produce perfectly undistOrled
Image and entirely nat and clear field has exacted
the largest amount OF study and skill which the problem
has called into exercise The complete solution Is only
obtained by combining the effects OF all the parts OF the
speak ono word is first necessary in regard to
| the phenomena OF vision. Inc eye is an opuca
| instrument. in which image is Regularly
formed as I'm the obscura The sensitive surface
on which this image falls IL called the retnd The eye
can accommodate Itself to the distance OF the object
within limits largely variable TO maintain the Image
the retna distinct The image the fetina must have
certain sze, very small doubt but ascertanabe. IN
order that may IL all AS the object recedcs the
Image dlminishes The light from IL at the same time
grows faint owing 10 these causes combined there Is
limit OF distance beyond which fail 10 perceive OBJ
jeots which themselves have appreciate magnitude
As object approaches the its image the retinn
grows larger, and points In IL, which, at greater dis
lance were below tho minimum risibe become percep