178 



SCIOPTICON MANUAL. 



EDGERTOX'S SELF-CONDENSIXU GAS CTMICDERS. 



" Special attention is asked to these cylinders, affording 

 as they do a more easy and safe means of producing and 

 condensing the gases for stereopticon purposes and gen- 

 eral illumination. To the traveling exhibitor they fur- 



Fig. 48. 



nish a compact means of transporting his gases, and 

 save the labor and vexation of carrying weights, pres- 

 sure-boards, etc.; while to the teacher they are invalu- 

 able, placing at his command, at all times, a powerful 

 light as readily started and as easily managed as that 

 of a coal-oil lamp. 



" They are made of wrought iron, with a cast-iron cap, 

 and are capable of sustaining a pressure twenty times 

 as great as the strain they are subject to. Referring 



