74 THE BOOK OF THE LANTERN. 



made of quick lime, and moisture will slake them. Lime 

 cylinders are difficult things to keep, for damp air will get 

 to them in spite of ordinary precautions. I have tried to 

 preserve them with partial success by dipping each 

 cylinder separately into a solution of indiarubber in ben- 

 zole or chloroform, which forms a skin upon its surface. 

 An American writer publishes a better plan. He melts 

 some solid paraffin or bees' wax in a metallic vessel, 

 exercising care that the heat is just enough to render 

 the substance liquid and no more. He then dips each 

 cylinder into the wax half way, allows it to cool, and then 

 holding it by its waxed end, dips the other half. This 

 coating, he says, quite excludes the air, and the limes may 

 be rolled in paper and packed away until 'wanted for use. 

 The coating is readily peeled off when the lime is required 

 for the lantern, provided that the heat employed in melting 

 the wax was not too high when the cylinders were dipped. 

 Each lime is cylindrical, and about one inch and a half in 

 length, with a central hole for the reception of the pin 

 upon the jet. This hole should be carefully freed of 

 powdered lime, by running a match through it, after 

 which the cylinder can be placed upon its pin, where for 

 the present we will leave it. 



As already indicated, the most commonly used form of lime 

 jet is the safety, or blow-through kind. If the jet be a 

 properly-constructed one, it will well illuminate a picture 

 15 feet in diameter. In this jet the hydrogen is sup- 

 plied from the nearest household source, by a connecting 

 tube of india-rubber. Herein lies, perhaps, its only dis- 

 advantage. In an ordinary house the connexion is an 



