188 ON SUPERHEATED STEAM. 



If water were always pure, no doubt many 

 elements of danger would be removed, as it would 

 take up tlie heat and generate steam in a more 

 uniform manner, and not decompose or weaken 

 the iron ; but as it is not only not always pure, 

 but always impure, every drop of the water carries 

 with it into the boiler an extraordinary mixture of 

 substances ; in fact, I believe that if you were to 

 take some water from four boilers, each boiler 

 being one from the four separate quarters of the 

 globe, and mix the water together, you would find 

 something of everything that is in and on the 

 earth. You would find all the gases, all the metals, 

 and all the earths so called ; and this is the mixture 

 which people boil up together under a great 

 pressure and at a great heat, and are then sur- 

 prised they cannot get uniform results. Of course 

 not ; for at high temperatures the organic matter 

 has influences, the nitrogen of the aerated water 

 has influences ; the lime, the metallic oxides, the 

 silicates, the sulphur, the potash, all have influ- 

 ences. 



A steam-boiler may be likened, with great 

 truth, to a man's digester, which has to deal with 

 multifarious substances, and gives the human 

 doctor as much difficulty as the boiler does the 

 steam doctor. If both were fed with jpure ma- 

 terials, less danger and less wearing would be 

 found in both cases. 



Havinof considered as well as I am able in the 



