Mechanical Science. 225 



together produce a cylindrical chamber, with hemispherical ends ; 

 they are stamped by a punch, so as to have the necessary groove 

 running round each pair ; and the two lialves, when put together, are 

 tied with a piece of string, or a copper wire, passing through two 

 holes at the extremity of the cartridge, so as to form a hinge, which 

 permits the case to open longitudinally when the string or twine is 

 unwound. — Trans. Soc. ArtSy xliv. 89. 



7. Elastic Mould for Castings. — Being much engaged in taking 

 casts from anatomical preparations, Mr. D. Fox found great diffi- 

 culty, principally with hard bodies, which, when undercut, or having 

 considerable overlaps, did not admit of the removal of moulds of the 

 ordinary kind, except with injury. These difficulties suggested to 

 him the use of elastic moulds, which, giving way as they were with- 

 drawn from complicated parts, would return to their proper shape ; 

 and he ultimately succeeded in making such moulds of glue, which 

 not only relieved him from all his difficulties, but were attended with 

 great advantages, in consequence of the small number of pieces into 

 which it was necessary to divide the mould. 



The body to be moulded, previously oiled, must be secured one 

 inch above the surface of a board, and then surrounded by a wall of 

 clay, about an inch distant from its sides. The clay must also extend 

 rather higher than the contained body; into this, warm melted 

 glue, as tliick as possible, so that it will run, is to be poured, so 

 as to completely cover the body to be moulded ; the glue is to 

 remain till cold, when it will have set into an elastic mass, just such 

 as is required. 



Having removed the clay, the glue is to be cut into as many pieces 

 as may be necessary for its removal, either by a sharp-pointed knife, 

 or by having placed threads in the requisite situations on the body 

 to be moulded, which may be drawn away when the glue is set, so as 

 to cut it in any way that may be required. 



The portions of the glue mould having been removed from the 

 original are to be placed together and bound round by tape. 



In some instances it is well to run small wood pegs through the 

 portions of glue, so as to keep them exactly in their proper posi- 

 tions. If the mould be of considerable size, it is better to let it 

 be bound with moderate tightness upon a board to prevent it 

 bending whilst in use ; having done as above described, the plaster 

 of Paris, as in common casting, is to be poured into the mould 

 and left to set. 



In many instances wax may also be cast in glue, if it is not 

 poured in whilst too hot ; as the wax cools so rapidly when applied 

 to the cold glue, that the sharpness of the impression is not injured. 



Glue has been described as succeeding well where an elastic mould 

 is alone applicable ; but many modifications are admissible. When 

 the moulds are not used soon after being made, treacle should be 

 previously mixed with the glue (as employed by printers) to prevent 

 it becoming hard. 



JAN. — MARCH, 1827. Q 



