( 136 ) 
flask (Comm. N°. 14 § 5), the liquid was sucked over partly into 
the condenser through the tube # by means of the cock 4, and the 
beaker B, was then filled up with liquid oxygen and remained so }). 
All these operations were watched through the observing-glasses and 
proceeded without offering the least difficulty. 
3. The arrangement of a Brotherhood air compressor for the 
compression of gases, to be kept free from admixture with air. 
In Communication N°. 14 this was dismissed in a few words. Plate 
II gives a view of the compressor with its separator and the newly 
devised accessories ('/, nat. size). As for the pump itself, in Plate 
III (!, nat. size) figs. 1 and 2 what has been newly added is indicated 
with thicker lines. By means of figs. 1 and 2 together, completed 
by fig. 3, the construction and working of the compressor may be 
understood ®). As explanation we may remark, that the cock B, 
supplies the steam, which drives the miniature steam-engines By, Bs 
on. 
placed at both sides of the body of the pump. When working at. 
full speed the shaft B;, which moves the plunger of the compressor 
up and down makes up to 500 revolutions per minute. Usually the 
air to be compressed is drawn directly from the atmosphere, through 
the suction-valve d, d — which is in the shape of a flat ring en- 
closed between two concentric circles — in which process it becomes 
mixed with water and a lubricant. To suck a gas which must be 
kept free from air this valve is covered with a head, consisting of 
a brass ring e, a thick observing-glass e, and a caoutchouc-tube e, 
which is firmly and hermetically fixed to both by means of bands ez and 
ez and cement *). The lubricant mixed with water, which in the case 
of the compression of N90 (and also of Og) was glycerine with 2/3 
of water, drops from the tube f} *) and the gas is supplied through 
the tube g, (Pl. HD. It also sometimes happens as will appear 
later on, that liquid is let off through this supplying tube. In order 
to prevent in such case the observing glass, through which we wish 
to watch the regular working of the valves, from becoming dull the 
screen g, has been introduced. Received through the sucking-valve 
1) Through 2, the measuring-condenser is exhausted, by means of Z, and Xs we 
may judge of the difference of pressure required to suck over the liquid from 
B, into m. 
2) E. g. by following the letters ag the circulation of cooling water may be traced. 
3) The metal-cage fig. 4 serves to prevent the projection of the glass in the possible 
case of accident. 
‘) In compressing air we might use spermaceti oil with water, but in the case of 
oxygen and nitrous-oxide explosions might then be dreaded. 
