TRANSACTIONS OF THE SECTIONS. 
59 
Formula; of three terms for alcohol and rather and of ‘two terms 
ind petroleum, were found to represent the results of Dr. r P - t i, c 
these fluids as closely as could be expected from the degree p 
These investigations were published in the 'Edinburgh New Philosophical Journal 
for July 1849* , , . .1 
M. llegnault having recently published an extensive series of expenmen s oni le 
pressures of the vapours of aether, sulphuret of carbon, alcohol, essence P 
•i'*» and chloroform (Comptes Rendus, 14 th August 1S54J, t he author - P! 
r, nnul;e of the land proposed by him, of three terms, to these expenm * 
Krsent paper states the results of these investigations, and gives a ta e o ' , 
Dms in the formula; far the pressures of the vapours of the nve Uuii s a f ’ 
'.octther with those for water and mercury, formerly determined, J he . 
*«r and mercury are slightly modified to adapt them to the position . 
l-’t‘ zero now considered most probable, that lormerly adopt© >y 
•“dug been 0-6 of a Centigrade degree lower; but this modification causes no p 
hnlly appreciable alteration in the computed pressures*. n e 
The degree of closeness of the agreement of the formula; wi h - 
'«periment, corresponds in a remarkable manner with the degree ofponty Utwmcn, 
»** ***•<*. «» fl-d.fobutari. is??”; 
sther above that temperature ; for essence of turpentine (which u g 
io cealar change by boiling), the formula is not applicable brfow - 70 J 
for chloroform (which it is impossible to obtain absolutely P ure h 
-'ji igradc ; but above these temperatures the agreement is very sat ‘®, ac 
'^ author shows that, although the densities of the vapours of the seveni fluids 
red to are known only by conjecture, the formulae lor them maximu p 
^ ord the means of computing for each fluid the function r being the mechanical 
°. f tlle latent heat of evaporation at any given temperature of so mneb 
i ' f S 15 “ ecesaar y t0 in the state of vapour, a space greater than it mis 
h< I Uld Bt nte by unity of volumet- 
On Mechanical Antecedents of Motion, I feat, and Light. 
By Professor W. Thomson, M.A., F.RS. 
r| ‘ !( hiiuica[ I)mUn ' Ca ' , ' <Jn Was °P enetl with some general explanation^ t ^ e 
*a‘m& forin\ ner6 'i’ antl the termB which have been introduced Q up 0 f 
^tlies, h~ ler which il I s manifested. Any piece of S'° lUot io U Vithout 
^tcr na i „ . 0r connected, which either is in motion, or can g‘ . 0 f motion 
Mvb c a T ance * huawhat * 9 culled mechanical energy. ^, e ^energy of a 
"dynamical energy" or "actual energy. filled 
^Ciai y l em at ,, re9t ' in virtue of which it can get into the 
1 ; I, 1 of a sL" ei 5-’- ihe author showed the use of these te >^i various 
l lr **ttatin n » °A mer 9y> and conversions and transformations ® . A as potential 
1 'irgv. 9tone at a height, or an elevated reservoir of ' ac tnal-energy 
i t , hc st °ne be let full, its potential energy is converted ^ a t the 
entirely as the actual energy of ^to 
f " ,t on th/ii* 8t , rikps * and is transformed into heat at the m channel, its 
''■■'•ntinl ene S r„°v ni If the water flow down by a gradual r rd i ng to an 
^jniiable ls gradually converted into heat by fluid fnc > ago, 
^tCfcrymade by Mr. Joule of Manchester the 
, ed t0 greatest reform that physical science has cxperiencea 
fci Tll * ,b Iir£| e,C L C0,,ftanta I® published in llie Philosophical 1JI* UlnSSTofVapours 
I ? lhcir hiU heei1 »ucce«afUUv applied to the computation of ‘' ,c . of Edinburgh, 
bruar y i9t h "i85r or evn P orori ° n - >" ■ rc ° d to ihe B ° y<a } 
