TRANSACTIONS OF THE SECTIONS. 
47 
mtnre was taken off from one of the chronometers, and it was placed m the ceiitre 
iftbeboxwhich contained the twenty others. The difference of its indications from 
lieothers give, bv an easv reduction, the mean change of temperature m the »nter- 
nL After two riionths’ Work witli the chronometers, the difference between the 
laatudes of Greenwich and.Mten was determined to be 0 39 46 *151, 
?SeerrorofO"-012; and thus the total difference between Poulkoya and ^jeen- 
^was 2 ®l' 18 ''- 674 ,with a probable error of only0"-057, care having been taken 
to determine the personal errors of the observers, and every other circumstance 
iliicli could ioflaence the result. 
CHEMISTRY. 
On the Regtihtion Combustion. Jiy N. -4rnott, F.R.S. 
Tsi author, after noticing the many applications of heat which require regulation, 
nd the advantage of giving this regulation by mechaoical self-acting arrangements, 
tecribestbe latest of these arrangemi-nts which he has completed, viz. the bi^nce 
•iIm, which is more easily maile and managed than the thcrmoinctnc regulator. 
This valve acta not by changes of the stove temperature, tike the thermometer 
wl't.bBtby the impulse or fora* of the entering current of air, and under all fluctua- 
hWiofthechiraDcy-drftUghl it admits only the aamc uniform stream of oir, and ^bte 
kgrefit or small, according to the adjustment made for the time. So perfect is the 
taiforpityof combustion thug effected, thut the quantity of coal to he consume is 
^ermiaed to within one pound in twenty-four hoars, without fiirthcr watemog or 
*lt{[itioD, after the stove is charged and t(ie valve is ndjuated as desired. 
ile hilanced valve regulator consists esaeotiully of a small weighbeam and sca es 
to placed digt oue scale becomes a flap air-door to the stove. ABC D m the dm- 
marks the beam and scales clistiiigu ished by jotted lines. On one of the .scales, 
A,tk regulating weight is placed, while on the other. D.the impulsoor momentum 
ihe eutering air (indicated here by Bniall arrows) acts as a countervveight. is 
fireutersbythc opeuing R and F in’the external case or shell 0 PQR of the 
reaching openings iu the internal tube G111K LM, which leads directly to the 
tofl-piland fire beyond S. As ibc rntering air obeying an ordinary cliimnev^draugn 
ftwagh the fully open valve exert# more force on the scale D than is sufficient o 
"Mbalance the weight placed in the scale A, it depresses the scale D. but m doing 
•' it St the ?arae rate U obatructine the aperture G H, by which the air has o pas 
inntr tube and fire, for the scale D then becomes a closing flap or door to tne 
'^iagof ihe internal tube: and the atrcom of air that con enter at tlie ex 
“ff door E F above is lessened by the closing of this inner door beneath, until 
tu much gets in as by its irainiUc juet balances the weight lu the &ca • 
this cbnditiou, thiugB cannot ebauge ao lung as the chimney-draught continues, 
tod the free spore for the passing nir will become less when the draught is s ro g 
^ Iwger when the draugM ia weak ; but the impulse and the quautiiy of air w 
the same so long a# the rerulatiiig weight is tlie immc. 
k a further to be afascrvrd, howevt'r, that the total force of the chinin y- ,? 
ftes^e B is made up of two ports,—Ut, the impulse of tlic „„;gg. 
describMl, which vnrieB exactly as the quautity yf -i.;tnnev 
H2=dlr.urtl.e ateadv, tram,mUar/,W, as it is called, of the P^^^ial chimney 
which ia a beat^ chimney is always acting whether air be cutermg or not 
i# .trongvst when the klvc comVlotely closes fur a time, second 
Jrtwwould often by suction bring a single plate D close to the ^ 
there. shutUng the passage altopetheJ if means were found to pravent 
^ ^carrence. U is%> neutralil' altoW‘r thi^ N 
PW) that, instvail of one internal door D, two are ^4; ^ 
^ so placed that this action on the one is in a direction exacth the 
thv other, and therefore each destroys or ncutra izes tl« f 
bemg of the same size) ; and the only force remaining to lift the regulating 
