REPORT ON MINERJiL. AND THERMAL WATERS. SS 



in the memoir already referred to*, T explained the mode in 

 which I conceived these substances to iind their way to the 

 surface. 



It seemed to me probable, that each portion of warm water, 

 from below, as it rose to the surface of the vvell or reservoir 

 which received the overflowings from the spring, would set at 

 liberty a little of the earthy and ferruginous matter it had held 

 in solution, in consequence of the disengagement of some of 

 the carbonic acid witli which it had been surcharged whilst 

 under a greater pressure. ' 



But this solid matter, being entangled in the Confervse float- 

 ing on the surface, would be prevented from becoming precipi- 

 tated ; and would form, by degrees, an earthy and ochreous crust 

 upon the water. 



But Professor Ehrenberg, of Berlin, to whom we are in- Einenbcrg'; 

 debted for so many striking discoveries with respect to recent lesearcbes 

 and fossil infusoria, has thrown quite a new light upon this |'o^P'^'^""S 

 subject, having ascertained, as he lately assured me, that this 

 red matter is in fact composed of the outer sheaths or coverings 

 of a multitude of little infusorial animalcules, which appear to 

 possess the singular property of secreting oxide of iron as well 

 as silica, and hence thrive only in chalybeate waters, which 

 afford them the material for the coat of mail Avhich invests 

 their softer parts. This at least he finds to hold good with re- 

 spect to the red fevruginous matter which collects in certain cha- 

 lybeate waters in the neighbourhood of Halle, and I have little 

 doubt that the same will apply to the similar incrustation found 

 in the water of Vichy, &c. 



Thus, whilst one class of beings requires, as we have seen, 

 for its existence the presence of sulphur in such a state of com- 

 bination, as is found to be absolutely destructive to other kmds of 

 life, another class secretes iron, a substance equally unsuited for 

 the nourishment of the great majority of animals ; as if it were 

 intended, that there should be no class of inorganic productions 

 which did not minister to the wants, and favour the production, 

 of a corresponding order of organized creatures. 



It seems worth inquiry, whether the red ochreous sediment Colouring 

 found by Davy in the baths of Lucca may not have arisen from '"a'fei- oi 

 a similar cause, and be made up of an accumulation of infusoria; plained. 

 and likewise whether the colours which belong to certain speci- 

 mens of I'ock-salt, which are sometimes of a deep-blue, but more 

 generally red, are not owing to certain vegetable or animal 

 matters. 



* Linnean Trans., vol. xvii. 

 D 2 



