OF THE 



IVERSiTY 



_^S * Salts. 133 



traction. The prominent surfaces of the cry- 

 stals first formed round the sides, draw up the 

 solution, and then expose it to a stronger evapo- 

 ration. Hence an addition of projecting cry- 

 stals, which, proceeding in the same action, 

 form a series of irregular capillary tubes, always 

 full of the solution, and always lengthening, till 

 a siphon is formed, by which the remainder 

 may even be drawn out. All this may be pre- 

 vented by slightly greasing the inside of the ves- 

 sel above the liquid. 



Enthusiastic chemists, observing the con- 

 cretion of salts shooting into such fantastical 

 figures, formerly imagined that the salts still 

 retained the vegetative powers of the plants from 

 which they were produced, and supposed even 

 that they saw the form of the plant in the cry- 

 stals ; but all this is absurd. The best vessels to 

 set solutions to crystallize in are those of a 

 globular form, the edges converging at top, as 

 that of an old retort with the neck broken. The 

 process of crystallization is not only employed 

 in separating salts from water, but sometimes 

 from one another, where they have no remark- 

 able attraction for each other. If two different 

 salts are dissolved in the same fluid, by applying 

 a certain degree of heat, that salt which has the 

 least attraction for water will, on some of the 

 water being dissipated, crystallize first, and 

 leave the other suspended. In this manner, by 

 repeating the evaporation and crystallization, 



