1813.] 



for evaporating saline Leys-, 



tain from 100 to 300 gallons English wine measure. The form 

 at bottom is nearly a semicircle; they are used in tlie West 

 India islands for evaporating the solution of sugar^ and from long 

 experience are found well adapted for this purpose. 



The boiler A Plate IV., is a representation of one of these 

 vessels capable of containing 300 gallons ; the depth is 2 feet 7 

 inches^ and the width at top 6 feet 2 inches : the bottom of the 

 vessel is set in solid brick-work bedded witii fire-clay, as repre- 

 sented in the drawing, to the depth of the dotted line B. The 

 space between A and B is the vacancy where the flue encircles the 

 boiler to heat it, which communicates with the vent E E for the 

 escape of the smoke. I'he boiler is kept constantly full of the 

 solution which is evaporating above the dotted line A, so as it 

 may not be in danger, when heated, from the cold solution which 

 it may be necessary to add to it. 



After the saline solution is so far concentrated that the 

 salt begins to form on the surface, from the peculiar manner in 

 which the boiler is built up, it is evident that the boil must pro- 

 ceed from the circumference to the centre ; and the salt, from 

 its density falling down as it is formed, is deposited under the 

 dotted line B in a loose state ; and when a sufficient quantity is 

 thrown down it is drawn out by the workman with iron ladles 

 formed on purpose. 



From experience we know that salts with a proportion of an 

 earthy basis (such as sulphate of lime) when evaporated in 

 boilers built up in the common mode, with the fire-place di- 

 rectly under the bottom, are deposited, and encrust the bottom so 

 much as to be with difficulty detached from them ; and when 

 these deposits increase to any degree of thickness, from the 

 vibration of the boiler, by the increased temperature, it is fre- 

 quently rent when least expected. 



On the contrary, when boilers are built up in the manner 

 described above, no accident has ever occurred of this kind with 

 me for more than two years ; and I have during that period built 

 up boilers which were formerly so much rent at the bottom as to 

 be no longer useful, but when placed on a bed of fire-clay, sup- 

 ported by brick-work to the depth of the extent of the rentj 

 were rendered completely serviceable. 



As to the expense of fuel — until the vessel is brought to the 

 boiling temperature, a strong heat is necessary; but for the 

 continuance of the boil and evaporation, a (ire of coal dross is 

 sufficient, when proper attention is given by the man who has 

 the charge of these boilers. 



I am, Sir, 



Your most humble servant^ 



Wm. Ramsay, 



R 2 



