( 635 ) 



cation in vacuo. The co^'e^ /S^g has been tightly screwed on the 

 hollow rod S^^^o and presses the glass S^^^ hermetically on to the 

 packings. B}^ means of the winged nut S^^^ the point is adjusted 

 so that the oil drops regularly through tiie openings >S'i„„i into the 

 space >S'i2^ wiiich communicates with /S'l^^ tJH'ough S^„.^ aiul which 

 may be watched Uu'ough the glass windows in /S'l^^. For our j)iu-pose 

 the oil holder S^^ is placed on a stout tube /S'^ onto ^vhicll by 

 means of india rubber i-ings and tightening bands the glass cylinder 

 Sii is fixed on a copper bottom, soldered to S^^. The glass cylinder 

 is fdled with oil and covered wdth a lid 8^5. By means of S^^^ new 

 oil can be admitted from the reserve vessel into tiie lubrication 

 vessel. In this way the air is sufficiently prevented from entering 

 the lubrication apparatus. 



Lastly, between the exhaust tube j and the compression tube' p 

 a safet}^ ^-alve has been placed, which prevents the pressure on the 

 compression side from rising above a certain height (usually ^/^ atmos- 

 phere). Hence it is possible to let the pump work on and to open 

 and shut the cocks as the work requires. The noise of the safety 

 valve gives warning that the cocks have not been properly used. 

 In any case no difticulty is to be feared if the possible output of the 

 pump might diminish in any w^ay in relation to the intake. P'ig. 4 

 shows a diagram of this connection, some of the parts being drawji 

 to proportion ; fig. (^ shows a section of the safety valve case itself. . 



The side tube />i is connected by a joint K with the tube i\ 

 wdiich opens into the space belo^v the safety valve. The space above 

 the safety valve communicates with the exhaust tube through the side 

 tube jj. The broad valve v^ is coated at the bottom witii an india 

 rubber sheet which presses against the narrow rim i\. The spring 

 v.^ is stretched with the key v^ while the plate i\ with the nut Vg^ 

 and packing is tightly screwed on to the rim v^^. The packing 

 cylinder i'„, like the packing just mentioned is kept under oil ; a 

 CQver v^^ above it protects it from dust. 



The connection K between the tubes j)^ and )\ could not be brought 

 about with flanges or with screw joints without causing tension in 

 the tubes. Therefore it was made in the following manner as shown 

 by fig. 5. A widened piece k^ is soldered on jj^, i\ fitting into 

 this piece. The india rubber connection ^-3 is kept in oil ; for this 

 purpose a rim l\ \\as used which was soldered on to p^ and a 

 rim k^ wdiich was soldered on to z^. Ovev these rims a wide piece 

 of tubing k^ is dra\vn which is fastened to k^ and /., by means of 

 india rubber rings /tg k.^ and tightening bands, and forms together 

 with these an oilreservoir. 



