746 



SCIENTIFIC RECREATIONS. 



box folded uniformly. They can also be used in omnibuses or tram-cars, 

 and tickets may be given by the machine on payment of the proper sum of 

 money. 



We will close this chapter with an illustration of a spiral bottle, which 

 can be done in the manner now to be described, so that the bottle will 

 actually become a glass spring. 



Take a mixture of 1 80 grammes of lampblack, 60 grammes of gum 

 arabic, 23 grammes of adraganth, and 23 grammes of benzoin. Make these 

 ingredients into a paste by the addition of water, and fashion a pencil of the 

 charcoal thus obtained. This pencil, when heated, will cut the glass wherever 

 it is applied. 



The process is commenced by scraping the bottle with a file and 

 following the instrument with the red-hot pencil. Wherever the hot pencil 

 is applied, the glass will be cut as shown in the illustration herewith. It 

 will be necessary to blow upon the heated pencil to maintain the incan- 

 descence as long as possible. The bottle as cut and representations of the 

 instruments are given in the cut (fig. 873). 



Fig. 873. Spiral bottle. 



