24 



ATTAINMENT OF VERY LOW TEMPERATURES. 



In some of my earlier experiments I was considerably troubled by 

 the presence of impurities in the hydrogen, and at last traced the trouble 

 to this source. For some time I managed to get over my difficulties by 

 replacing the low pressure cup-fiber each time I compressed hydrogen, 

 but as this proved troublesome and unsatisfactory I resolved to modify 

 the low pressure cylinder so as to completely eliminate all chance of 

 further trouble. 



Fig. 7. — Hydrogen compressor. 



The alterations were carried out by Brin's Oxygen Company. The 

 new arrangement of the cylinder is shown in fig. 7, B. The length of 

 the cylinder and of the studs which keep the cylinder cover in place 

 was increased by 87 mm., the length of the stroke, and a second piston 

 gg, with bronze rings of the usual pattern was introduced between the 



