CH. IV] MAGIC LANTERN WITH THE LIME LIGHT 101 



ture of thorium and cereum such as is used in Welsbach mantles 

 have been employed. Nothing gives a more brilliant incandescence 

 than the unslaked lime, but it deteriorates rapidly by absorbing 

 moisture when exposed to the air. This is not the case with 7/ircon 

 and thorium ; the discs of these may be used over and over, some- 

 times hundreds of times, while with the limes one usually has to put 

 a new one in place every time the lantern is used ( 153 a). 



FIG. 56. MAGIC LANTERN WITH THE 

 LIME LIGHT. 



(From the Catalogue of the Enterprise Opt. Mfg. Co.). 



The door of the lamp-house is open, showing the burner with the lime in 

 position. 



H The hydrogen supply tube, extending to the burner. 

 The oxygen supply tube, extending to the burner. 



154. Oxygen gas in steel cylinders. This is now a great 

 article of commerce. Nearly every large drug store keeps one or 

 more of them in stock for the use of physicians. The steel cylin- 

 ders for containing oxygen were formerly large and contained 

 oxygen under a pressure of about 17 atmospheres (250 pounds per 

 square inch). Such cylinders are still used; but at the present 



153a. There has lately been introduced a substitute for limes, known as 

 Guil Pastils. These are rather soft white cylinders of a substance giving 

 great brilliancy when used in place of lime. The Guil pastil is put into the 

 holder so that the end is heated, hence the lamp should be in the form shown 

 in fig._ 57 K, not as in fig. 56 or 59 L. The Guil pastil serves for 10 to 20 

 exhibitions. It is composed mostly of a zirconium compound and is not hurt 

 by exposure to the air. It should be heated up gradually as directed for the 

 limes ( 162). Moving Picture World, June 13, 1914, p. 1539. 



