New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1906-03-05
PHOTOGRAPHIC MICROBES. (.
Use Of Ultraviolet Rays Antedates the Ins
Vention Of DR. A. Koehler.
To the Editor OF The Tribune.

To the Editor OF The Tribune
Sir: An editorial IN your paper OF yesterday. en-
Titled "Photosraphing Microbes. betrays some con-
fusion OF IDEAS concerning recent inventions IN
microscopy Its writer attributes the adaptation
OF ultraviolet light TO ARCHAEOLOGICAL Investigation
to Sedentopf and Szigmondy, OF Jena. Now. as A
matter Of fact, these gentlemen have. within tbs
last few years devised interesting apparatus for
the observation OF ultrarnicroscopic particles but
this IS not accomplished by OF ultraviolet
light; furthermore a method has been worked
at Jena for the application OF ultraviolet light
such purpose. but it's inventor is Dr. A KoehIer.
The instruments designed for both processes
products OF tho same establishuent-the Carl Zefss
Optische Werkstaette-and IS not surprising that
they should be confused. but the principles In
volved are distinct The method OF Siedentopf
and szsmondy employs visible light. which Is used
TO illuminate particles immersed IN a liquid By a
transverse BEAM IN the manner that a sun ray
through a crack IN dark room renders apparsns
the notes in the air.
The idea OF using ultraviolet light for micro
scopical purposes probably dates much further back
than the construction of Dr. Koehler's complicated
and costly apparatus. ultraviolet glass" which.
like quartz differs from ordinary glass by prop
erty OF transmitting the invisible rays spec
trunn. was commercial article optical purposes
as long November. 1903 and how naEcn
earlier do not pretend TO say. 1t is to be re-,
marked that IN Dr.. Koehler's apparatus Light from
an electric spark Is resolved by a prism and tbs
ultraviolet rays intended for alons selected
from the spectrum
While II is true that ultraviolet rays do have
more effect a sensitive plate than ordinary rays
do not think that this fact has any special sig
nifcance in connection with the present work and
Ths real vaas Of a 9e s OF @ o &
ton OF minute particles believe LES in the suPs-
rtor resolving power due TO its short length
on this point few words OF explanation need
studied in school, and which regard Hght travel
ling In straight lines are true only 50 long al the
dimensions than the wave length Of the light en-
iost sight Of bV trrFaction and ais sets per-
ceptbIe limit TO the resolving OF microscopes
extended 10 fner particles n we can get IEht 81
lesser wave lengths and this Is possible by en-
II may Be questioned whether Photographic as,
distinguished from subjective Observation Is any
With edna light except that from the naturs
Of the case it is rendered necessary the rays be-
i ms p bn7ysve in nnIing that DR. KosIsr IA
devised means whereby indirectly the object IN
the microscope may bs xswsd cnn,s Consists Is IN
fuorescent screen which ernits visible rays under
the 9ct9I q The invisible sges 1t is I9ts4ssd
light has been found 20 have peculiar property OF
resolving otherwise unseen details OF orsainio
New-York. Feb. "A. 1908
lin some press accounts the two improvements
here referred to-a mode OF fIluminati ton which
assists visual work and the OF ultraviolet
light for photography-have been so associated
that II was natural TO infer that Professors Sci
dentopt and Szigmondy originated them both
There Is a greater need for correcting thar i'm
preston in regard 10 the one last mentioned. be-
cause in the recent descriptions OF Professor
Ernst's experiments az Harvard University the
reader was left TO suppose that he was the ap-
thor of the systern-1