LIMESTONE 305 
Test for its solubility in water, and ascertain that it is 
practically insoluble. Heat strongly some of the rock in an 
iron pipe. When cool, place the pieces on a tin dish, and 
pour some water over them. Observe that the whole 
becomes very hot, that steam rises from it, and if the proper 
quantity of water be used, that the rock crumbles to 
powder. The heat applied to the rock drove off the Carbon- 
dioxide, and left the Lime—commonly known as quick- 
lime. The water subsequently used was absorbed by the 
quicklime with the result that the substance became 
slaked lime. 
Uses. Limestone is obtained in many parts of New 
Zealand, where immense deposits of it occur. The rock 
is burnt in kilns and coverted into Lime, which is used 
in making mortar or as a dressing for soils. A soft kind 
of the rock known as Chalk, is used for writing on the 
blackboard—and for marking wood. When finely-powdered 
the same material is employed in making tooth-powder, 
or is known as Whiting; by mixing it with oil it forms 
putty. | 
A granular Limestone, known as Marble, is used in 
buildings and for making monuments, table-tops, mantle- 
pieces, ornaments, etc., etc. 
The only use made of Limestone in New Zealand is to 
convert it into Lime, which is employed in making mortar 
and as a dressing for soils. In several Limestone forma- 
tions in New Zealand good samples of granular marble 
occur. These, however, are not worked. 
Stalactites and Stalagmites. In almost every 
Limestone district, certainly in every district where there 
are Limestone caves, these formations occur, 
Water containing an excess of Carbon-dioxide in solution 
possesses the power of dissolving Limestone. ‘The Carbon- 
dioxide necessary to convert it into a solvent is acquired 
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