42 Mr. West on Natural Waters. 



I exposed a weak solution of gelatine to similar treatment, 

 with correspondent results : the greater part was separated in 

 the same manner ; the water evaporated left little but the salts 

 contained in the jelly. I ascertained that common clay pro- 

 duced, by allowing longer time, the same changes in appear- 

 ance, and that the weight of the dissolved matter was less than 

 before ; but I could not easily free the clay so entirely from 

 salts as to bring the proportion separated to the same degree 

 of certainty by weighing. 



2. On the deposition of Sulphate of Lime from Hard 

 Waters, and on the Solvent Power of Hard Waters. 



Sulphate of lime, being held in waters by its own solubility, 

 cannot be wholly separated by mere boiling : on applying heat 

 to its solution, one of two effects takes place : if the evaporation 

 is slow, the solution is left more concentrated and stronger ; if 

 it be boiled briskly, the solution may remain of the same strength 

 though not saturated, while a portion of the sulphate separates 

 in a solid form. The manner in which this proceeds is curious ; 

 the property is common in a greater or less degree to all sub- 

 stances difficultly soluble, though lime itself is the most strik- 

 ing instance. When a bubble of steam arises, the salt which 

 was dissolved in that portion now vaporized, separates in the 

 solid state ; and as such bodies require not only a large portion 

 of water, but a long time to effect solution, before this is again 

 dissolved, many other particles are separated, and thus the 

 quantity deposited goes on increasing, the strength of the so- 

 lution itself remaining all the time nearly the same, though any 

 difference which may take place is of course in the way of 

 increase. 



Thus in the production of ' fur, 1 in the vessels in which it is 

 boiled, the sulphate of lime acts about as speedily as the car- 

 bonate, and probably more injuriously. In many operations, 

 therefore, it becomes a very serious evil. I was assured at 

 Manchester that it was necessary frequently to empty the engine 

 boilers, and chip out the crust formed, in some cases as often as 

 once in six weeks ; the labour of effecting this, and the hin- 



