The Pupil Teacher: Avignon 



windows set in ribs and rosettes of stone. At the 

 back were huge raised benches, with room for an 

 audience of many hundreds; at the other end, where 

 the choir once was, stood an enormous chimney- 

 mantel; in the middle was a large massive table, 

 corroded by the chemicals. At one end of this table 

 was a tarred tub, lined inside with lead and filled 

 with water. This, I at once learnt, was the pneu- 

 matic trough, the vessel in which the gases were 

 collected. 



The professor begins the experiment. He takes 

 a sort of large, long glass bulb, bent abruptly in 

 the region of the neck. This, he informs us, is a 

 retort. He pours into it, from a screw of paper, 

 some black stuff that looks like powdered charcoal. 

 This is manganese dioxide, the master tells us. It 

 contains in abundance, in a condensed state and 

 retained by combination with the metal, the gas 

 which we propose to obtain. An oily-looking liquid, 

 sulphuric acid, an excessively powerful agent, will 

 set it at liberty. Thus rilled, the retort is placed 

 on a lighted stove. A glass tube brings it into 

 communication with a bell-jar full of water on the 

 shelf of the pneumatic trough. Those are all the 

 preparations. What will be the result? We must 

 wait for the action of heat. 



My fellow-pupils gather eagerly round the ap- 

 paratus, cannot come close enough to it. Some of 

 them play the part of the fly on the wheel and 

 glory in contributing to the success of the experi- 

 ment. They straighten the retort, which is leaning 

 to one side; the blow with their mouths on the 

 83 



