New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1868-07-30
SCIENCE.


PORoDs CARBON.-A correspondent of Ihe
london Chemical Nei0s gives the following description
Of the manufacture Of porous Carbon In various shapes
at Paris mixture OF wood charcoal ana amman 0har
and dried at steam heat; while the material IS sim
warm 90 per cent of tar added When cold certain
smount OF asphatum is added and the is pressed
mods The proportions In which the ingredients
are used vary according to circumstances. The mold
cd objects placed in boxes of sheet iron and covered
all over with mixture OF sand and charcoal afterward
ohey are heated on the sole OF furnace Gases Whch
disengaged during the operation are burnt IN he l
Tue entire operation lasts about "a hours Carc1u
attention is required during the ealcinatOn the pppe
hes OF the carbon depend IN great measure upon INC
management of this part of the procedure.
GREAT BRIDGE OVER THE OHIO RIVER
The iron railway bridge in course OF construction be-
tween Louisville Ky, and JefesOnylIe, IND, VIII De
these viii be $40 feet EACH and six 256 feet each Ex
eeptng on the longest spans the rails VIII be placed on
che Pink description of the truss is here quoted
Fom paper American Iron Bridges" read by Mr..
eolburn before the London Institution of Civil Engineers
In this bridge pair of diagonal tension bars connect
the foot Of the principal strut or kgpOst in each truss
with the ends O the top chord This pair of diagonal bars
supports of the whole weight of the truss and its load
Each half span is subdiyided by strut and two diagonal
tension bars extend one to the nearest end of the top
shord and the other TO the top OF the center post Each
quarter span Is again suodyded into eigths ana theSe
again ioT spans greater than 100 teet INTO slXtee IN
truss OF tins KIND having l6 panels the weight OF inc
bottom OF the strut nearest to either OF the piers dstD
nted as follows Calling the weight one one-half Is trans
teTTed directly through tensOnTOd to the nearest emu
end Of the top chord and thus upon the pier The other
hall is carried TO the top Of the second strut nom tDe
and Is received at the bottom of that strut by Pl oil
OneOurth being taken directly TO the nearest pier whale
the other fourth is transferred to the top of the strut az
the quarter span. This fourth is again SuOdyded a e
foot of this strut eighth being transmitted through
tensOnTOd to the nearest pier, while the 0theI elgh
passes to the top of the middle strut OF tue whoe span
and is received at foot of this strut by the main ten
sion-rOds which thus transmit OF the Original
lead pier Thus the weight at the loot or te mrs
from the end OF the truss is distributed as fol
lews ODe-ha OnefOurth, one-eighth OncsiXeenth, or
In all 16sxteenths of that weight reach the top OF me
pier through four cOpYcrgng sets OF ehSOhou
while the remaining sixteenth reaches the opposite pier
strut through the Intervention of three separate systems
of tensOnbars. With the exception OF the lo99 AT te
foot center strut which load is decy
TO the piers the loads at the bottom OF the yette
less subdivded In the manner Just deseoeu
before reaching the ends of the truss Inc esuDated
sSst OF TINS Sdgf wa e Is 70 nc o Se work -
Alfred Fink, and the AssstaDtEngneer, MI f. W.
Vaughan
REFRACTIoN OF LIGHT.-DT. Gladstone lately
presented the Royal Institution Of London the results
Of researches relating TO the retroactive ndces
Of different substances, showing how the INDEX varies
with temperature BY means OF an electric lamp ne
threw the yellow line IN the spectrum OF the metal sodium
on sereen and used hollow prism hled with the Oh o
nutmeg the refTacting medium This oil was selected
because ITS temperature is very readily changed but any
ether oil will the purpose The prism was Xed
1t it's angle of minimum deviation the position OF the
yellow band OF the spectrum was marked by strp OF
Black paper. On stirring the oil with heated metallic
rods it's temperature increased and tine yellow so
dun line was shown to be less reiracted imam before
tlades that all liquids have their index Of refaction d.
Miushed by heat
He had also turned his attention to solids but on find
ing that the retroactive index of crown glass WAS not
changed by heat he discontinued his Investigations but
F1zeSn OF France had since discovered at IN hSly Al
the retroactive index OF solids is increased by heat
the two exceptions noted by him being crown glass,
which altered and uOr SPAR which has its refrac
tive power diminished by heat.
DR. Gladstone and the Rev. Pelham Dale, while expert
meutng together had discovered optical property
which was constant under varying temperatures and
common 20 sOhd liquid, and gaseous conditions, namely,
tle specific retroactive energy that is 10 say the refrac
tive index minus one divided by the density The spe
energy multiplied by the atomic weight OF body
will give us refractOD equivalent Tables had
pnted by the lecturer showing the atomic weigs OF va
elementary substances and their corresponding re-
Gactiyc equivalents which then exhibited. Com
pound bodies generally possess the mean lefraotlng
power of their constituents BY experiment was shown
that on mixing spirits and water the resulting hqmd
gives little refracOn than either OF these sub
stances before mixture, owing 10 slight contraction IN
bulk when spirits and water are mixed the increased re-
fraction being due entirely 10 increased density. The !
the reflaetOp equivalent of any substance whether
mixture or true chemical cOmPOund is the sum Of the
1tladVtlto cquiF"Snts OF it~ eoaStii neuts p,
The substance of greatest dspersive p0 o knnvcn
Is melted phosphorus Next to it stands OXycnUSe ~
yanadini, then oiiows sulphur IL might DO aslsd Why
SEINE substances such as Iceland spar, double re-
naetmS DR. Gladstone believed such substances have
may be 9ra elRS ae - in dile79gs To
anee 10 the passage q Aht Consequently on dssoiviIg
such substances the property of double refraeuon should
disapPe@r sueh on experiment Is FOUND 10 DC the Ic
the solutions Of such crystals only one image which
about the mean OF the two seen in the solid
~Gue Of the most beautiful experiments made by DE-
<ladstOn6 the formation of ice flowers. slab OF
lee cut atle to the plane of freezing was placed III
front 0f the electric light, and greatly magnhed by
means a lens As the Ice began 10 melt the flowers be-
gan TO appear growing like stars on the screen As Dey
were enlarged circle oval appeared III the middle OF
each star These beautiful and symmetrical flowers be-
como visible because water refracts light differently from
dense consequently occupies less space imam the Ice
from which made vacuum is formed IN the middle
nause Of the cireular or oval appearances