PENCIL-HEADS. 39 



ARTISTS' INDIA RUBBER. 



It would seem hardly possible to improve upon the properties 

 of the native gum, for erasing pencil marks, all things considered, 

 and yet the vulcanized article has peculiar properties, which 

 are desirable in some cases. It is made of three qualities, the 

 gritted sponge compound, which is very soft and yielding ; the 

 gritted magnesia compound, which is very hard, so that it will 

 retain an edge or point, and very nearly answers the purpose of 

 a knife for erasing ; and a medium quality which is gritted, and 

 , resembles nearest the native gum. All these kinds are sharper, 

 or cut faster than the native gum, but being less adhesive, that 

 which is removed from the paper does not adhere to them, but 

 has to be blown off, on this account they are thus far objection- 

 able. 



The durability of these kinds of erasive gum, makes them 

 applicable to the pencil-heads hereafter described, for which 

 the native gum would not answer so well. 



PENCIL-HEADS. 



These are made of the artist's India rubber before described ; 

 they are set into metal sockets, as represented in the plates, 

 figs. 1, 2 and 3, or are formed into rings or heads which are in- 

 tended to slip over the ends of a wooden pencil or crayon of any 

 description, as represented in figs. 4 and 5. The advantages to 

 be derived from these pencil-heads are these : viz. being attached 

 to the head of the pencil, they are always at hand for instant 

 use, and are convenient either for the pocket or the desk, and 

 though so very small, are so durable as to do the service of 

 pieces of native gum many times larger. 



