428 Transactions. — Chemistry. 



alkaline taste of soda-water, and lias evidently built up, by its continuous 

 depositions of the calcareous matter wliicli it holds in solution, the whole of 

 the white-crusted mound which surrounds the pool. 



"It may assist the imagination of the reader if he fancy a painter's 

 palette, magnified to a diameter of fifty feet and placed on a low piece of 

 New Zealand swamp and fern. The palette will represent the white mound 

 formed by the calcareous incrustation, the thumb-hole, the bubbling spring. 

 A wavy line drawn from the thumb-hole to the further extremity of the 

 palette is the gutter by which the overflow escapes. 



"The deposit from the water is of two distinct Idnds — the principal 

 calcareous, and forming the bulk of the surrounding incrustation ; the other 

 is soluble in water, has a cau.stic taste, and is found only during dry 

 weather as a recent white efflorescence caused by exposure to the air, or as 

 little starry groups of crystals in the water of the gutter (soda ?). The 

 water is highly charged with carbonic acid gas — as much as five ounces by 

 measure of this gas having been obtained from a soda-water bottle full of 

 the water. That both water and carbonic acid gas (otherwise ' foul air ' 

 or ' choke-damp ') exist deep in the earth's crust, is a fact well-known to 

 every miner on the Thames. Deeper still than our mines have penetrated, 

 what water there is must be under a great pressure, and thus rendered 

 capable of absorbing a very large quantity of the gas. When thus super- 

 charged with gas, it has the faculty of dissolving carbonate of lime in 

 considerable quantity, and if it comes in contact with that substance under- 

 ground will rapidly take it into solution. Suppose now the water, charged 

 to excess with carbonic acid gas, and thereby holding carbonate of lime in 

 solution, to force its way to the surface of the ground : The pressure is 

 taken off; the gas escapes bubbling at the spring; and since the lime can no 

 longer be held dissolved, it de^Dosits itself wherever the decarbonized water 

 runs from its fountain. Such a deposit is formed in New Zealand around 

 many a less fascinating spring than that of Puriri, and we have found at 

 such places mossy and other incrustations which rival the similarly grown 

 travertine of Europe. Three other little bubbling springs were found in 

 the immediate vicinity, all very small, and not one having any zone of 

 incrustation. 



" Until a proper chemical analysis shall have been made, it is impossible 

 to form an opinion of the value of this spring as a medicinal agent. That 

 its mineral, gaseous, and other constituents possess some valuable proper- 

 ties, I should think there can be little doubt; and when these are better 

 known it is possible that the medical men of the Thames and elsewhere 

 may be not unwilling to recommend its use to their patients in certain 

 diseases for which it may be found beneficial." 



