PROCEEDINGS OF THE rOLYTECHNIC ASSOCIATION. 475 



In the town of Chester, 27 miles from Springfield, and near the railway 

 leading- to Albanj'-, is an immense bed of emery equal to that of Naxos. 

 Tiic emery trade had been monopoli/.ed by two houses in Liverpool. In 

 this country there is a great deniand for emery on account of the large 

 number of liru arms manufactured here. The emery of Chester is situated 

 in the very heart of the arms-manufacturing establishments. It is found 

 in tV\'o mountains, north and south mountain. It is found 750 feet ab#ve 

 the Westfield river. The widest part of the vein is from ten to fourteen feet 

 thick, but the average is seven. It has been traced about four miles. It 

 will doubtless in time supercede the great monopoly of Asia minor and 

 control the market. The supply may be regarded as cxhaustless. 



Dr. Jackson illustrated the geological formation by a drawing on tlie 

 blackbt)ard. On the upper side is first mica slate, then soap-stone, below 

 that talcose rock, talc, crystaline talc, talcose slate, chlorite slate, then 

 emery. On the opposite side of the emery is very beautiful hornblend, the 

 handsomest he had ever seen. The effects of segregation are seen here 

 distinctly. There are immense masses of round fine emery surrounded by 

 a mineral called margarite. Pure emery is crystalized alumina and iron. 

 Sapphire is pure alumina and ranks in hardness next to the dTamond. The 

 chemical analysis of the emery of the south mountain is: 



Alumina .- 4.5.50 



Protoxide of iron 43.00 



Silica and titanic acid 11.50 



100.00 



It was discovered by means of margarite. This is called useless, but it 

 was the guide board which led to this discovery, as it is always associated 

 with emery. When he first saw it he supposed it was a bed of magnetic 

 iron ore, but when he found the margarite he at once declared it to be 

 emery. Emery is very diflScult to break with the aid of heat, but it is 

 crushed or separated under pressure quite readily. At the present time 

 emery is sold at Naxos at $140 per ton, and here at $300 per ton. 

 The emery is of different grades; the flour emery is made by mixing 

 it with water several times and separating the finer particles. The largest 

 kind, used at the Springfield armory, is about tiie size of a grain of wheat. 

 Emery wheels are made by mixing emery with valcanized india rubber. 

 They are the most powerful wheels known for cutting metals. Emery is 

 largely used in polishing granite and porphyry columns. The ancient 

 columns of Greece are as perfect to-day as when first erected. There are 

 no mosses or other disfigurements growing on them because there is no 

 chance for the water to enter the pores of the stone. There are numerous 

 places in this country where porphyry can be obtained. And in the course 

 of time we shall have in use tables of Porphyry which cannot be scratched 

 and tombstones that can never be covered with moss. Solid sapphire and 

 crystals of corundum have been found in the state of New Jersey, but 

 emery in (quantity has never been found in this country before the recent 

 discovery at Chester. 



Dr. R. P. Stevens cquired whether the Professor had any theory as to the 

 manner in which these metamorphic rocks associated emery were cryscalized. 



