646 PHILOSOPHICAL TRANSACTIONS. [aNNO 17 11. 



made very strong: to this hemisphere I procured another, of burnish brass 

 exactly made, to fall with its brim about an inch within the glass, that I might 

 the better cement them together; which I did securely from any ingress of the 

 air in that part. Thus, when joined, it became nearly a globe ; only the dia- 

 meter through its axis, was somewhat more than its transverse diameter, which 

 was a disadvantage to its strength, as the sequel of this account will show. In 

 this manner I exhausted all its air, at least nearly so, and then put it on the 

 machine to give it a circular motion, as usual in such experiments. On apply- 

 ing my hand to the brass hemisphere in motion, no light could be discovered 

 within : I then rubbed it with a deal stick, but the success was the same. After- 

 wards I applied a piece of sealing-wax, which has in itself a very electrical 

 quality : this wax, rubbing roughly on the brass, seemed to shake the parts of 

 it ; yet not any the least glimpse of light appeared. I then held the flame of a 

 candle to the brass in motion, which something more than warmed a circle on 

 it; hoping by this means to excite or obtain some discovery from it. Yet, 

 though a smart attrition was made on that part, it was altogether unsuccessful. 

 Being tired, I let in the air, and suspended my further trials till the following 

 night. At which time, when I had exhausted the air from within the globe, I 

 began the attrition with a coal cinder; which being somewhat rough, I thought 

 it might shake the parts of the metal, and put them into such a state or mode, 

 as to exhibit an appearance of light ; but this, and whatever else I then tried, 

 was to no purpose. In this exhausted state I left the globe on the engine, to 

 consider a little what further trials to make ; with what bodies, and in what 

 manner to proceed with them : but to my great surprise, in about an hour after, 

 being in the next room, I heard a noise almost as loud as a musket when fired ; 

 and immediately coming into the room, I found the glass of the globe broken 

 all to pieces, and the brass hemisphere on the ground ; which I took up, and 

 found several bruises it had received from the violent strokes of the broken 

 glass, which had dispersed itself in pieces all over the room. A large looking- 

 glass, at least 3 yards from it, was cracked almost from top to bottom, and quite 

 across the middle, by a blow from a fragment of it ; for where it struck the 

 glass, the cracks proceeded from it every way, like so many radii drawn from a 

 center. From these experiments we may safely conclude, that if there be any 

 such quality as light to be excited from a brass body, under the fore- mentioned 

 circumstances, all the attritions of the several bodies used for that purpose, 

 have been too weak to produce it. And indeed, considering the closeness of 

 the parts of metal, and with what firmness they adhere, entangle, or attract 

 each other, a small degree of attrition is not sufficient to put their parts into 

 such a motion, as to produce an electrical quality; which, under the fore-^ 



