g52 YORKSHIRE ALUM WORKS. 



fectly cool, in the summer season. The casks are then taken 

 to pieces, and a holiow cask qf alum is produced ; it is then 

 broke into, and the whole of the saturated solution of alum 

 (called tun wacer) is removed back into the pans, to go 

 through the process anew. 



This last process i« called roching-. The outside of the 

 cask of alum is now to be cleared from dirt, atid the sedi- 

 ment which is deposited at the bottom. It is then broken 

 up into masses ready for the market. 



Practical ohserv.aiio)is and remaj-ks upon the foregoing prO' 

 cesses. 



Method of as- The method pursued by the ahnn makers to find the spe- 



certauiing the j,-j^^ gravity of any liquid is capable of considerable accu- 



specific gravi- ° ■ . 



ty. racy. A bottle is procured, that will contain about i of a 



pint. The narrower the neck, the more accurate will be 

 the r€sults obtained by it. This bottle is balanced in a 

 pair of sensible scales, we will suppose it to weigh 1000 

 grains, it is then filled with distilled water, and carefully 

 dried with a cloth ; now allowing the water to weigh 2400 

 grains, this last number is divided into 80 parts or penny- 

 weights, and we have 30 grains corresponding to one penny- 

 weight; this they subdivide into ^ and ^. Hence we may 

 ascertain the relative specific gravity of any liquid. 1 pen- 

 nyweight is equivalent to 1*0125, and 80 pen ^yweights to 

 2*0. Care however is necessary, to have a counterweight of 

 3400 grains, equal in weight to the water and bottle toge- 

 ther, which must always be put into the scale, along with 

 the other weights, in operating. This was formerly a great 

 secret among the alum makers, and they sold the method 

 at a high price, or handed it down to their children as an 

 hereditary possession. 

 Improvements Considerable advantage might be derived to the manu- 

 "gges e . faciurer, by reducing the size of tlie fire places, and erect- 

 ing iron doors, to prevent a current of air passing over the 

 fire, mstead of entering by the ash pit : a, very material 

 saving of fuel would arise from adopting this method. 



A very material errour is committed, by concentrating 

 the liquor in the pans to near the specific gravity of 1*5, 



and 



