300 CEMENTS. 



powder, ulong with a little red-lead and borax, or 

 with the borax only. 



Cement for Derbyshire Spar and other Stones. 



A cement for this purpose may be made with 

 about seven or eight parts of resin and one of bees- 

 wax, melted together with a small quantity of 

 plaster of Paris. If it is wished to make the ce- 

 ment fill up the place of any small chips that may 

 have been lost, the quantity of plaster must be in- 

 creased a little. When the ingredients are well 

 mixed, and the whole is nearly cold, the mass 

 should be well kneaded together. The pieces 

 of spar that are to be joined must be heated 

 until they will melt the cement, and then pressed 

 together, some of the cement being previously 

 interposed. 



Melted sulphur applied to fragments of stones 

 previously heated by placing them before a fire, 

 to at least the melting point of sulphur, and then 

 joined with the sulphur between, makes a pretty 

 firm and durable joining. 



Little deficiencies in the stone, as chips out of 

 corners, &c. may also be filled up with melted 

 sul})hur, in which some of the powder of the stone 

 has been melted. 



A Cement that will stand against boiling Watery and 

 eve)i bear a considerable Pressure of Steam. 



In joining the flanches of iron cylinders, and 

 other parts of hydraulic and steam engines, great 

 inconvenience is often experienced from the want 

 of a durable cement. 



