TRANSACTIONS OF THE SECTIONS. 187 
temperature, it follows that, in case of maximum effect, or the temper- 
ature of best condensation, 
é =~, that 1s an. 
ce c 
Now ¢ is 1000; and if the steam in the boiler be at 5 lbs. above the 
atmosphere, or if e = 40 inches of mercury, and ¢ = 1, 
40 
= ——_ = 0°04. 
tai cea 
Again, if the steam be at 73 Ibs. = 45 inches, 
45 
= — = 0:045. 
SSD Ts laa 
Again, if the steam be at 10 Ibs. = 50 inches, 
50 
= —— = 0°05. 
“= 7000 
Hence we find, that the best elasticity or temperature in the con- 
denser depends on the elastic force of the steam in the boiler. 
With steam of 5 lbs. in the boiler, the elasticity of maximum effect 
in the condenser is 93° Fahr., and the best vacuum on the barometer 
is 28. 
With steam of 7% lbs. in the boiler, the elasticity of maximum effect 
in the condenser is 95°, and the best vacuum on the barometer is 27°8. 
With steam of 10 lbs. in the boiler, the elasticity of maximum effect 
in the condenser is 97°, and the best vacuum on the barometer is 27°6. 
In like manner it would be found, that with steam of 50 Ibs. in the 
boiler, worked expansively, as in Cornwall, the best vacuum in the 
condenser would be about 26° on the barometer. 
It is hoped, therefore, that engineers will not in future distress them- 
selves at finding the vacuum of their condenser much less perfect than 
the vacuum of others who have obtained 30 and 30% inches at so great 
a loss of fuel and power. To obtain a vacuum of 294, with the weather 
glass at 29°75, and steam at 73 Ibs., would be to sacrifice four horses’ 
power out of every hundred. Ina day when the barometer is as low 
as 284 inches, the vacuum in the condenser would indicate 26°8. In 
speaking of the vacuum in the condenser, it would save much ambi- 
guity to indicate the elasticity merely of the steam in the condenser ; 
thus, if the barometer stand without at 292, and the barometer of the 
condenser at 28, it might be stated that the steam in the condenser 
stands at 14, being the point of the maximum effect. The indication 
would convey at all times more precise information. 
Mr. Russell stated that the President had just put into his hands a 
communication in French on this subject from M. Barnes. Instead of 
a jet playing inside the condenser, M. Barnes allows it to rush in sud- 
denly, and then stops it by a slide-valve. 
