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The Museum Gazette 



HOW TO MAKE A THORN-HOUSE. 



You do not know what "a thorn-house" is? No. Nor 

 perhaps have you any definite idea as to what is meant by 

 " the preservation of twigs." No. Well, attend and we will 

 try to make them clear. There are such things as salt springs. 

 The water with salt in solution comes bubbling up though 

 a rift in a limestone rock. It is, however, only a weak brine 

 and how to get the salt out is the problem. Boil it down you 

 will say. Right ; but cauldrons and coal are expensive, wood 

 is scarce, whilst there are thorn-bushes in plenty on the hill- 

 side. Make a thorn-house. This is to be done by building a 

 large gabled shed near the spring but on a lower level. This 

 shed is fitted with a framework upon which bundles of small 

 branches are laid in a slanting position. The water, conducted 

 in pipes or gutters to the highest frame, is liberated by per- 

 forations and is allowed to trickle through the bundles, to be 

 caught again in a gutter below. Owing to free evaporation 

 only about half of what was put on at the top flows out below, 

 but it is much stronger in salt. The process is repeated 

 through another thorn-house at a yet lower level, and finally 

 through a third. The brine is now strong, almost at satura- 

 tion point with its salt, and a very slight employment of 

 artificial heat will be sufficient to make it crystallise. 



If the bundles of twigs thus employed were rapidly destroyed 

 the process might still be troublesome and expensive. The 

 twigs, however, do not decay rapidly, nor do they become 

 encrusted with salt. The bundles in the first two houses 

 require to be changed only every four or five years, but those 

 in the lowest will last seven. They are, so to speak, pickled, 

 and do not decay. Those in the first house take out certain 

 salts of lime which the water contained and become crusted 

 over until they resemble branching coral, or specimens from 

 the Knaresbrough dripping wells. They fortunately take it 

 all and send to the lower houses a purified brine, and one 



