New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1878-12-07
SCIENCE FOR THE PEOPLE.

A CURIOUS CHURCH.-The church at Bex, in
Switzerland in which the Helvetic Society held It's
meetings last year. presents IL Is SAID curious acOus-
teal phenomenon. The interior Of the building IS rect
angular in shape except that one OF the short sides Is
replaced by rounded part The pulpit is nearly at the
middle of OF the longer sides Of the rectange Now
persons seated opposite the pulpit heard speaker near
the bottom of 1t "a little TO right very badly But
any one situated two or yards from the middle Of
the rounded part on the side OF the door, heard with
markabe dstinctuess the words pronounced from
below the pulpit ReciprOcdy, words spoken IN very
low voice from the rounded part perfectly heard at
the point occupied by persons addressing the audience
NODDED. IL of conjugate acoustic force me
effects in this church at Box are said TO be more rrmaI
able than those in Paul., LOnOn or the ConSCrYa-
des Arts ct Melters Paris often cited in works OIL
physics.
THE BLUE Process OF COPYING TRACINGs.-
In a short paper read before the Institute OF Mining
Engineers Mr. p. Barnes gave the following SUMMARY
of the mauipulations required in this process l. ITO
vide fat board large as the tracing when Is 10 nc
copied q Lay on this board two or three hcknesses OF
common blanket, or its equivalent TO give shghlly
yielding backing for the paper g. Lay on the blanket
the prepared paper with the sensitive side uppermOs
4. Lay this paper the tracing. smoothing II out as
perfectly as possible TO insure perfect contact
with the paper. 3. Lay the tracing pate OF cehl
glass which snonld be heavy enough TO press the trac
Ing close uOWD upon the pdpcI' OIhlhdiS
in thickness quite sufficient 6. Expose the whole 10
clear sunlight by pushing it out shelf from au
ordinary window or in any other convenient way or
six to ten minutes. If clear syligt only can NC "u
the exposure must he continued for thirty or foynVo
minutes and under cloudy sky sixty TO ninety minutes
may be needed T. Remove the prepared paper ana
drench it freely for two minutes in clean WAFER
and hang up by one corner to dry. Any good nara
paper may be employed (frOm even leaf rom press
copv-book I'D 10 Bristol boardJ which will bear the
necessary wetting For the sensitizng solution take
l7s OF. citrate iron and ammonia and 8 o. clean
water and Also III red prssate OF potash ana o.
clean water; dissolve these separately ana NIX taco,
keeping the solution In yellow glass bottle or cAleuy
projected from the light The paper may DC very Cou
vrgieny coated with sponge Of four luches d'ctrl
with Que fiat side The paper may he gone over once
with tue sponge quite MOST with the solution ana
second time with The sponge squeeze very Gry. dne
drawer, aud must be shielded rom the Igt ulCi
II 70 20 80 ftr he eyrore TO the nrht the sur
face becomes darker bronze, and me lines OF lhe IHhg
appear as s;ill darker on the surface Upon Washing
the paper the characteristic blue tint appears with the
lines Of the tracing IN VIVID contrast
NITROGEN IN ELECTRIC LAMPs.-It is prob
ably we'll understood that Sawyer Man use
carbon pencils, made incandesCent by a con-
tinuous current and enclosed in closely sealed glass
tube in atmosphere OF nitrogen gas These inventors
nave found that the carbon however lasts long ume
IN nitrogen but they have only recently been 'ble 10
explain why IL uOes not dsL III d NdCuuH' 'nIN'''J
when as In the Koun lamp, one carbon pencil has
already burned up and disappeared, converting the
minute quantity OF oxygen remaining IN the vacuum
INTO acid gas II no oxygen Is eit why shoud
the second carbon disappear in few hours also Fon-
tame said that the disintegraon was due TO sort OF
evaporation" Sawyer says that this Is not co. lie
SAYS the oxygen Of carbonc acid leaves the gas
having greater affinity for substances in state Of III
tense ncaBdescence The carbon in the gas Is deposited
and the oxygen IL set free to burn the heated pencil
This process would forever or as long as thero
an iDcandescent carbon 10 attack In the Konn lamp
deposit OF carbon IN an extremely nne dnt Is iouhu ~,
evapOratiOn of the cray Sawyer claims that II
tIeopv ~ correct the permanency OF heated carbon
an atmosphere of nitrogen from when me oxygen 10
absolutely excluded seems a very reHsohaDie ca'n
Color BLINDNESS DEFINED.-Mr William
Pole writing IN Nature thus explains the true limits
and nature Of blindness In the first place we see
white and black, aud their intermediate or compound
raytproyded they are ireefrOm alloy with other coor
precisely as others do Secondly. there are two cooTS
properly so called ramey, yellow and blue, which ALSO
II uuaoyed we Sec so be ascertained In the
normal manner But these two are the only co ors oI
which VIC have any sensation and hence the defect mas
been given by Sir John Hcrschel the scientific name Of
diehromic piSton But now the difficulty OF the
explanation. 1t may naturally be asked; DO we not
see objects OF other color such roses grass, voes
oranges and so on And If do them,what DO they
look kei The is that we do see all such things
but that they do not give the color sensations cor
recy belonging to them their colors appear to us
varieties Of the other color sensations which we are able
10 receive This will be best explained by examples
Take first the color red soldiers coat or SUCK OF
red sealiugwix conveys TO very positive scnsauog
of color BY which perfectly able TO identity. IN
Of instances bodies OF this nue. But Whch
/ examine more closely what l really do see, am
obliged 10 come to the conclusion that the sensation
perceive Is not that identify separately but Is
simply modification OF one OF my other sensations,
unueiy yellow. 1t Is, in tact, yellow shaded Win
black or gray-a darkenCd yellow, or what may call
yellow brown. find that all tho most common hues OF
red correspond with this description, ard In proportion
as thew are more scarlet tending toward olange
the yellow see ID more vivid The explanation, sup
nose that none such reds pure, they are com
binatOns of red with yellow so that see the yellow
element Of the combination while the true red element
is visible to Inc color, and acts only as darken'
ing shade.
INTEI L n ANE