164 Prof. Barnard on the Elastic Force of Heated Air. 
would be the effect upon the available power, of considerably re- 
ducing this. Still retaining the relative dimensions of the cylin- 
ers proposed by him, [ wi rst assume a compression in the 
supply cylinder to one-third _ eed _— This will give an 
absolute temperature of 8139-8, (= 35498 F.) which will be re- 
quired to be further raised to 1085.07 nt 626207 F.). That this 
temperature is admissible if it can be reache d, I have no doubt. 
y this arrangement we shall obtain a mean available pressure 
of 7°33 lbs. to the sq. inch, under an absolute pressure of 70:56 
Ibs., and with an economical superiority to the non- cone 
steam engine of five atmospheres, of nearly three to on 
But in “order to show that the economical advantages petongial 
to this method of employing air dre to a great extent attainable 
under much lower temperatures, I will suppose that Mr. Joule’s 
principle is applied to an engine working under the temperature 
upon which all my former computations were founded, viz., 
above the temperature of melting ice, or 482° PF. We find that, 
under this temperatue, when 7, is made equal to 7’, the mean pres- 
sure becomes 4°61 Ibs., and the absolute pressure 43-22 Ibs. to the 
sq. inch, while the economy, compared with steam, as above, is 
more than two too 
In the following: sioner statements, are exhibited at one 
view ail the particulars relating to the several cases under each of 
the three temperatures which have been considered. In these ta- 
bles 6 stands for the temperature, Fahrenheit, produced by com- 
pression; i. e., J == 7’—459°; R stands for the ratio of economy 
as compared with steam expanding from five atmospheres to one ; 
and R’ represents a similar ratio, steam of three atmospheres eX- 
panding to one being taken as unity.* 
= 1220°°7 = T61°7 F: 
Q 
: m Z Fr Pp R’ 
Joule, ‘750 250 9-85 10592 4569-5 3-436 5-031 
Max. m, ‘907-250 10-45 128-00 508°-7 3-631 5321 
Max. J, ‘750 -373 10°82 70°92 356°-0 2839 4:153 
Abs. max, 1094 -436 12:07 88°52 410°-0 2-502 3665 
* In order that a comparison may be made with gore Eriesson’s abandoned en- 
gines, in which he proposed to carry a pressure of 12 pounds (above the atmosphere) 
in his reservoir, while 7 was made =, we observe, fee that these conditions require 
a Bebstan J temperature of 592° F, which i is nearly equal to to the medium temperature 
proposed above. We shall 438 then for Ericsso 8 arrangement, 
vf! == 1051" == 592° F, 
m I bg scat R R’ 
‘667 “T50 4°35 27 156°6 1195 1-750 
These a of Rand R’ su no regenerator to be used. The epg 
if perfect in their action, woul coats R=3-153, R’ = 4-167. Allowing that 
fail to he see of 30°, asstated by Ca pt. Ericsson, the values would be R= 2668, 
Ris 
x 
