Basalt. 
279 
become rigid and gelatinous, and showed cubes of 
sodium chloride under the microscope. A portion of 
the finely-powdered rock was digested for hall an hour, 
with acetic acid, hydrochloric acid added to the filtered 
solution, and, on evaporating on a glass slide, cubes of 
sodium chloride were formed in abundance. 
In order to guard against the possibility of the 
sodium chloride being contained in the rock as an 
impurity, derived from its proximity to the sea, I 
determined the presence of chlorine in four separate 
samples of the basalt, in the manner recommended by 
Messrs. Fouqu4 and Levy. 1 A gram of the basalt was 
powdered and ground in an agate mortar, washed well 
on a filter with boiling water, and then acted on by 
nitric acid. The acid was evaporated to 'dryness to 
render the silica insoluble, and taken up with water; 
on the addition of silver nitrate a precipitate of 
chloride of silver formed immediately. 
There can be no question, then, as to the presence 
of chlorine and some easily soluble soda-bearing 
mineral in the Bondi basalt. 
The soda minerals found in basalt are — soda 
felspars, nepheline, hauyne and nosean, and analcime 
as a secondary product. 
The soda felspars do not gelatinise with acids, and 
certainly are not rapidly soluble in weak hydrochloric 
acid or acetic acid. So we cannot consider the felspars 
the source of the soda that crystallizes as sodium 
chloride. 
1 Mmfcralogie Mierographique, p. TH). 
