CHEMICAL MANUFACTURES ON THE TYNE. 181 



first-class iron ships. The rivets are carefully coated, and are thus pro- 

 tected from the corrosive action of the bilge water. It has been found 

 of equal service in sugar-carrying vessels, where the leakage of the 

 molasses exercises a very corroding action. 



Roman cement is prepared by calcining septaria in open kilns, and 

 afterwards grinding the burnt material in horizontal stoves. It is used 

 either alone or mixed with an equal volume of sharp sand. 



Keene's marble cement is made by soaking calcined gypsum in a 

 solution of alum, and then recalcining the mass at a dull red heat. Thi3 

 recalcined material is then ground and sifted. It is only used for 

 internal work, such as floors, skirtings, walls, &c. It is largely employed 

 in London in churches and club-houses ; it rapidly dries, after being 

 applied, and may be papered or painted in two days. When dry, it is 

 so hard that a nail cannot be driven into it. Two qualities are made : 

 one of which can be polished in imitation of marble ; while the other 

 is used as a ground for painting — when different colours are intro- 

 duced, a superior scagliola is formed. 



The quantities manufactured per annum, are as follows : — 



Portland Cement 



Roman ditto ... ... 



Keene's ditto 



Plaster of Paris 



The present prices are — 



Portland Cement 8s. 6d. per cask of 430 lbs. 



Roman ditto 7s. 6d. „ 336 lbs. 



Keene's ditto 14s. Od. „ 836 lbs. 



Plaster of Paris 30s. Od. per ton. 



Quantities and Prices of Raw Materials Used in Local 

 Chemical Manufactures. 



Tons. 



Casks. 



10,000 ... 



.. 50,000 



350 ... 



... 2,450 



50 ... 



350 



200 ... 



.. 2,000 







Price 





Value. 





Tons. 



£ s. 



d. 



£ s. 



Sulphur (included as pyrites 



) 72,800 



10 







109,200 



(Copper value not included.) 







Salt .... 



90,000 



15 







67,500 



Nitrate of Soda . 



2,500 



14 15 







36,875 



Chalk 



144,000 



2 



6 



18,000 



Coals . 



323,000 



3 



9 



60,562 19 



Manganese .... 



11,400 



4 







45,600 



Rough Epsom Salt 



1,500 



2 5 







3,375 



Magnesian Limestone 



700 



3 



6 



122 10 



French Limestone 



14,000 



4 



6 



3,150 



Resin .... 



— 















Tallow 



— 















