164 



STREET-MAINS. 



lead joint ; caulk into the bottom of the socket, to the depth of about two 

 inches, white rope-yarn well covered with putty ; then at the lip of the socket 

 caulk in tarred gaskets of such a thickness that it will just fit into the annular 

 space left between the pipe and the socket, and to such a depth, that a space 

 of about 1^ inch will be left Tbetween the two yarns all round the pipe. At 

 the top of the socket, where the ends of the tar-gaskets meet, draw up a portion 

 to form a " gate," exactly in the same way as for running a lead-joint. Take 

 two parts of melted Russian tallow and one part of common vegetable oil, 

 and pour the mixture, while it is warm, into the " gate ;" it will run into and 

 fill up the space between the two yarns. As the mixture does not contract 

 on cooling, and is quite impervious to the air, it must form an air-tight joint. 

 a is the tarred rope-yarn ; b the tallow and oil ; and c the puttied white yarn. 



Fig 39. 



Mr. Clegg adopted this plan when laying down his atmospheric railway, 

 knowing, from long experience, that lead-joints were not to be depended 

 upon ; but jointed upon the above plan, half a mile of nine-inch pipe was 

 found by the barometer to be perfectly air-tight, when exhausted, equal to a 

 pressure of twenty-four inches of mercury. 



When mains require to be taken up to be replaced by others, which is fre- 

 quently the case, the pipes may be drawn out of the socket without trouble ; 

 whereas, when the joints are made with lead, the pipes are obliged to be 

 broken before they can be removed, which causes a great sacrifice both of 

 labour and metal. 



