New-York tribune., 1870-09-19
SCIENTIFIC NOTES.

y SCIENTIFIC ROTES
Tar CONTINUITY OF THE GASEOUS AND
,n,1,n STATES OF MArTER.In paper on this suolect
,..a before the Royal Society of London Dr lhonas
,ares gives an account of various experiments mace
nv hm during q series ~ years, upon gases especlay
Ssibng the combined effects OF heat and pressure m
esrbonie acid gas a temperatures varying from 10 =,
sso O. and at pressures ranging from 4s to l0g 20
pberes. The temperature at which this gas and
touefy by pressure he finds 10 be 3092o c. or rs %
tis he calls the critical point ttS ARo9ss6 sssove HIS point
not occur at temperatures tte tteed so nv siight
very great change OF density If producem emoyements
alterations of pressure, aud the hiekerng % Of de
are conspicuous which render iaeI @ % . AS the direct
result OF his experiments ne ,d forms OF the
ss Condon Of matter and may made to ps pst the
another by series OF breach
81 eohtiputy From csrbonie acid as I'tiap NAV he
earbOnic acid perfect llquIG & and the gas and
srcomplshed hy continuous process ng series of con
fonid are only distant stages OF an5s of tempera-
tuons ehanges oCaTSope acid finds itself II tT9s IN
state OF instability and snduebst bSt with the evou-
.hahgs OF on " ~ The condition which, 10y the sohlnous
process only ee the question as to what is
SS Condition or state OF carbonio acd wS paes ~
dawn o the volume Of the liquid without giving
EVIDENCE during the process OF tne % , " %
tSis oIestion is 20 be found in the intimate relations
which subsst between the gaseous ana nqnd sates oI
cases are compressed 10 certain volume al tempera
lures below the critical point moeeniaE iorecs arr
volume and during this process 1t is easy to dlshgush
spsed from that which has changed its volume But
when the same change is effected by the cOnnuouh pro
eess the carbonc acid through conditions which
lie between the ordinary gaseous aud liquid states and
which have valid grounds for referring 10 the Que
rather than to the other Nitrous oxde hyur9chonSc
acid ammonia suphuric ether sulphde OF carbon, all
exhibited critical points when exposed nnder pressure 20
the required temperatures The author proposes Tor t1e
present arbitrary distinction between vapors and
gases, to conhne the term vapor TO gaseous % bSdes
al temperatures below the critical points, aud Whchi
theeore he hque6ed by pressure so that gas aud
liquid exist in the same vessel IN the one
another.
On THE CHANGE IN THE RADIATION OF HEAT
nv RoUGHsEss OF sURFACE-one of the last papers by
the late Prof Magnus had the above title and was pub
Hshed Berlin scientific journal II il one OF great
fun SUMMARY OF it "a our columns win admit. He com
his article with the statement that Leslie was
the first observe that body with rough surface
radiates more heat than body with smooth One anu
he thought this was conditional Gn the density Si ue
surface yet he urged against ts view the circumstance
that the limit between hard and soft BONES cannot pe
hxed. MellOni subsequently maintained that the
altered radiation depended merely on chdnge
IN the density OF me snpefInclsl ia! ,a!er tdt ,,nt
in certain substances, such glass; marble, agate,
found change the radiation whether the surface
was there an increase when they we're rongnened he
asespes & mes Is t1 t made by rolling or hammering
greater density the surface than in the inte
Tor. Looking at list of radiating powers OF bodies
is at once seen that general this property nversey
their respective denstes and as the different dens
ties OF one and the same substance In support OF ths
view he made the following experiment He constructed
aquadrangular box with metal bottom using Tor lts
sides four plates of silver two strongly hammered ana
two east and allowed 10 cool very slowly IN their mods
plates they were polished with pumice and char
coal without the use Of the hammer or burnisher then
Iseans OF soft solder The outside Of one OF the
east and one Of the hammered plates was then
strongly rubbed in direction with emery pa
per The sides which retained their uster reflected sharp
images the rubbed sides duh and sreaked ones The
silver vessel thus prepared filed with hot water and
the radiation Of heat therefrom reaching the thermo
electric pile the dehectOns OF the needle were for the
hammered
scratched side l the cast and polished side 1872 the
east scratched side lSo. Scratching the hammered
plate had thus produced increase OF radiation while
" IN the cast plate it had produced dimunition This un
Hpected fact appeared TO Meon 10 prove the correct
mess Of his principle We are as much and perhaps more
scratching than in saying with Meon that it becomes
less dense; for during the scratching pressure is
eted upon the surface and it be asserted that the
individual ratches not pressed in bat scooped ont
u this scOOpiLg pressure k eXeted upon the adjacent
state condensation. Prof. Manus alludes TO other
experiments made by Melloni and Knobauch which
20 confirm MellOni's views and then gives experiments
made BY the author WITH platinum PLATES instead cad OF cop
alterations also the surface, such produced
silver by sns quantities of sulphretted hydrogen.
As possible before rolling after having been heated radi
sted much heat as before; Here hardness cannot
have affected radiation Another platinum plate hsd
been passed under great pressure between two roll
treatment Of the sides exhibited small elevations
while the other remained fmooth Th% , af,er tbe
plate had been strongly heated, even this differ.
snce was no longer pereeptble Hence II follows
And even regularly aer1i9ting elevations ana depes-
siOns may exist without any increase in the radiation
When the contrary, plain platinum plate which
had been heated by glassbOwefs lamp and was quite
sor was rOughened by means OF dne emery paper the
radisiitn was doubled. When platinum plate was GOV
sred with thin iGyer Of spOpgy platinum, by spreading
hin Iaver of aminOrchOride of platinum upon H. anQ
then strongly heating, without treatment with Mrle
ard il indicated times much radiation as before
being treated with spongy platinum Inc author con,
sludes that the increase of radiation WIN f0nsneneI
snrface depends essentially the refracton Wch neat
experiences its emergelce from the surface OF rad
htng body The greater the refrsctve index OF heat he
Ween the Tadiang substance aud the air, the smaller is
the radiation from the plane surface, and then the
autity OF heat reflected inward increases, The metals
have doubtless very high refraeng index bence lbey
reflect the from without and allow bnt few 10 pfne-
trae and hence they reflect internally those coming
the interior and allow but few 10 emerge. Great
inequalities OF radiating surface do not occasion any
important alteration in the radiation. Sach only
when the radii OF curvature very small and
greatly, and when the Tadating surface has but
title diahermancy. In general the roughness OF tire
surface may effect both an increase and dimnutiOn in
abe radatiOns mt the inequalities are very fine and
yery deep, there il almost always increase IN sub
~aBees like metals. When there 10 very fine powder of
a.. substance almost rtdiaDg surface, the
Id, 'SG Is considerably increased.