THE BOOK OF THE LANTERN. 33 



several feet of good rubber tubing ; and a bag to hold the 

 gas when made. The retort which I prefer is Oakley's 

 pattern, and is made of wrought iron, brazed and rivetted 

 together, and of the form shown in the accompanying 

 sketch, fig. 16. It will be noticed that it is of conical form, 

 and that its lower part, where it rests on the stove, is con- 

 vex in shape. It terminates at the mouth with a brass 

 screw, and in this screw fits a branch, or pipe, which con- 

 veys the gas away as fast as it is generated. An important 

 point in this branch is the arched bend, immediately over 

 the retort, which obviates undue friction, and also prevents 

 any solid particles given off from the retort clogging or 

 stopping up the tube. With that provision one element 

 of danger is avoided. Another point of importance is the 

 little upright tube, or nozzle, immediately above that same 

 bend. This is merely a short piece of tubing fixed on to 

 the branch, and in which a cork can be fitted. This acts 

 as a simple safety-valve. Should the pressure of gas 

 become too great, the cork will fly out and no damage can 

 possibly occur, except the loss of a very small quantity 

 of gas. 



There are various other forms of retort which are used 

 and recommended by different operators. A cast-iron one 

 is, of course, more lasting ; but in case of accidental explo- 

 sion, its particles would be as deadly as those of a bomb- 

 shell. But such an explosion should never occur, if 

 ordinary care be taken. With some persons, familiarity 

 with the most dangerous agents so rapidly breeds con- 

 tempt, that they get careless in a very short time. We 

 may suppose that this happened in the case of an optician, 



