54 Guide to Belfast. 



a kind of clay known as bauxite, which is found abundantly 

 in County Antrim. The bauxite is first ground to quarter- 

 inch cubes, and is then calcined to destroy any organic 

 matter contained in it. The c dciner is an iron tube, revolving 

 at a slight inclination, which delivers the roasted ore through 

 a cooling tube to a second mill, where it is ground s'ill finer. 

 The ground bauxite is treated with a strong solution of 

 caustic soda, under steam pressure of loo lbs. per square 

 inch, forming a soluble compound called aluminate of soda, 

 the impurities remaining insoluble ; the mixture of aluminate 

 and caustic soda having remained in the pressure chambers 

 or "kiers" for about seven hours, a cock is opened, and the 

 pressure in the " kiers " blows the mass up to the filter- 

 presses at the top of the building. The aluminate is now 

 carefully filtered twice, to ensure the alumina being free 

 from iron, silica, etc., the residue from this process being 

 waste product. 



The separation of the hydrate of alumina from the soda 

 is effected by the addition of excess of hydrate of alumina 

 itself, and by constant stirring in large tanks provided with 

 agitators. This process takes about thirty-six hours, when 

 the agitators are stopped, and the hydrate settles to the 

 bottom. The hydrate is next pumped through filter-presses, 

 and thoroughly washed, to remove the last traces of soda, 

 and dried by forcing compressed air through the cakes which 

 it now forms. The dried hydrate is next calcined, to drive 

 off the water, and is then in the form of anhydrous alumina. 

 This product is very liable to take up water again, so it is 

 heated to about 2,000 degrees Fahr., which causes it to 

 crystallize, and leaves it ready for packing. 



This process is only the first step in the manufacture of 

 aluminium, the pure alumina being sent to the Company's 

 factory at Foyers, near Inverness, where the electric reduction 

 of metallic aluminium from this product is performed. 



Thread M.\nufacture. 

 One of the most important enterprises in the neighbour- 

 hood of Belfast is the thread works owned by William 

 Barbour & Sons, Ltd., at Hilden, near 1 .isburn. Founded 

 on a very small scale about 1 15 years ago, they have gradually 



