?o Proceedings of the 



grey, but waves of pure gypsum or alabaster are constantlj' met witb. 

 Bands of a clear fibrous cbaracter, from four to six inches thick, are also 

 met witb, following the general run of the strata, which is slightly inclined 

 to the horizon. Another variety abounds in large crystals of a pale 

 yellow, and has received the name of sugar-cacdy gypsum. The bard grey 

 takes a polish like marble, but owing to the existence of thin veins of shale 

 it is impossible to get a uniform lustre ; the same cause necessitates a very 

 oaref ul picking of the gypsum after baking, to present a dark tinge being 

 given to the plaster. 



Mr. Baxter then gave a description of the composition and nature of 

 gypsum, and of the various conditions in which it is met with, and con- 

 tinued as follows : — 



I will now give a description of the Sub-Wealden Company's works. They 

 are situated at Mountfield, Sussex, some three miles from Battle Station on 

 the Hastings line of the South Eastern Eailway. They were commenced 

 under great difficulties, as the materials and machinery for sinking the 

 shaft had to be carted over a hilly country, and in part over field roads and 

 through plantations, the cost of carriage being in winter as high as £\ per 

 ton. It was soon apparent that a good road must be made to the works, 

 and at last a railway' connecting them with the South Eastern Railway, 

 about a mile and a half distant, was decided on. This has been 

 carried out, and is now in full operation. The processes of con- 

 verting gypsum into plaster of Paris are three in number, viz., 

 the quarrying, raising, and sorting ; the baking of the stone ; and 

 lastly, the grinding and sacking. The beds of gypsum are fortunately 

 from six to seven feet high. In these seams headings are driven about sis 

 or seven feet wide, in which are laid tramways as the work proceeds. 

 The gypsum is drilled indifferent directions to a depth of three or four feet, 

 and in ihe holes blasting cartridges are inserted with time fuses 

 attached, so as to enable the miners to retire to a safe distance 

 and await the explosion. After blasting, the stone is placed in small 

 trucks or trollies on the tram-road, and shunted to the mouth of the 

 pit into a cage, whence the trolly and material are raised by steam 

 power to a height of some 30 feet above ground level. Here, by 

 means of a timber staging and tram-road, it is discharged on to the high- 

 level s> rting platforms. On the platforms the stone is passed through 

 po^-erful stone breakers driven by steam power, and then sorted. The good 

 stone is wheeled in barrows to the kilns and then baked for some twenty- 

 four hours. The waste is again passed through the stone breakers to 

 further reduce it, and sold for road metal, or the portions containing rough 

 gypsum are ground for manure. The operation of baking the plaster, though 

 apparently a simple process, is one requiring much care and attention. As 

 I have already stated, there are 2079 parts of water in gypsum ; now, about 

 20 per cent, must be driven off, but a small percentage, which we may term 

 ibe water of crystallisation, has to be retained. If the whole of the water 

 is drawn off, the plaster will not set, and becomes what is termed " dead ; " 



