LXII. NORMAN SELFE. 
The four diagrams, shewn by Fig. 10, illustrate graphically the 
comparative strains on the crossheads of an ordinary and an Ant- 
arctic Compressor respectively throughout one revolution of their 
DOWN STROKE 
SINGLE COMPRESSION 
ABSOLUTE PRESSURES 
Gs SGaOe es TEE Saas Peaks Sines Aire i Beas Sata 
$0 40 30 60 70 80 90 100 110 120 130 140 150 160 
O ¢o 
ATMOSPHER: 
Aine 
SECOND COMPRESS! 
tt Ri 
Fig. 10. 
shafts. A to B representing the down stroke and B to E the up 
stroke, working from 30 lbs. to 160 ibs. per square inch pressures 
(absolute). The length of the vertical lines shows the resistance 
offered to the piston in pounds per square inch, and pounds absolute 
if the area of the piston is taken as unity; which work in the left 
hand figures is all concentrated at the latter part of the up strokes. 
The dotted lines represent the adiabatic and isothermal curves | 
respectively, the actual curve of compression being assumed as 
half way between them. In the lower left hand figure the pres 
_Sures during the down and up strokes of an Antarctic Compound 
