40 



DENSITIES OF (JXYliEN AND HYDROGEN 



l> may jnojierly engage with eadi other, it is necessary that a should be held in a 

 definite jiosition whenever it dues not support h; accordingly, a tuJje pending below 

 in a hollow cone, is placed as shown. Wiienever e li is lowered, li\ and therefore /, 

 are raised, taking the position shown in Fig. 18; a and c are therefore both 

 suj)poi'ted or both freed by a single motion of the handles seen in Fig. 10. 



Kjc. i8. — One arm of revolving carrier, loworcil, hooks engagcil. 



The object carrier e h slitles vertically upon a sleeve /. A collar u is attached 

 to e It so as not to turn with it, and is moved veitically by the lever p. But e h 

 also rotates with the sleeve I, and the motion of both is produced by the worm n 

 and the worm gear m which is fixed to I. Bv the rotation of id and tlie motion of 

 J9, any one of the six hooks l> can be put in any lU-sircd position. The sleeve / 

 turns on a stud which is screwed into the plate ;• /•. 



Fig. I'J is a plan of the reversjil mechanism seen fii)ni above, the stoue cover 

 being supposed removed, and the plate r r, by which the apparatus is attached to 

 tlie stone cover, being indicated only in dotted outline. The worm gear, also, is 

 broken away to show parts beneath it. At the centre of the plan is seen the hollow 

 stud which is screwed to the plate ;• r. The worm and gear are shown at m n. 

 The lower end of the sleeve is fixed in the disk .s; to this is attached the radial arm 

 t which carries at its end a stud u wliicli compels the object carrier to turn with the 

 sleeve and the woi'in gear: p is the lever l>y which <■ ]i is raised or lowered; it 

 receives motion from a crank on the shaft w, which also moves the arm //, by which 

 in turn are moved the arms k h. 



When the carrier has brought two opposite hooks exactly into position, two 

 jirojcctions c e are I'cady to enter two notches in the latches x ./', which, being 



