308 PHILOSOPHICAL TRANSACTIONS. [aNNO ] 706. 



affording but a weak light, yet the manner of making them seemed to open a 

 way to further improvements, which, during the late interval of meeting, I 

 have pursued with my utmost diligence. The results of the many experiments 

 made on this occasion are comprised in a very few, which shall be repeated be- 

 fore this honourable Society, as opportunity shall permit. 



One is as follows: I took a glass globe, about 9 inches diameter, and having 

 exhausted it of air, took it off from the pump, having first turned a cock, to 

 prevent the air from re-entering it. Thus secured, and fixed, to give it motion 

 by the great wheel, described in Phil. Trans. N° 304, which when turned gave 

 a swift motion to the globe, on whose surface was applied my open and naked 

 hands, which in a very little time produced a considerable light. And still as I 

 moved my hands from one place to another, that the humid effluvia, which very 

 readily condense on glass, might be discharged from every part of it ; so the 

 light improved, till words in capital letters were legible by it. At another time, 

 when I made the experiment, the light produced was so great, that large print 

 without much difficulty might be read by it: and at the same time, though in a 

 pretty large room, the whole became sensibly illuminated ; so that the wall at 

 the farthest distance, which was at least 10 feet, was visible. The light ap- 

 peared of a curious purple colour, and was produced by a very slight and tender 

 touch of the hands, the globe at the same time hardly being sensibly warm. 

 Nor do I find that a more violent attrition increases the light any thing. Nor is 

 the highest degree of rarefaction of the air in the globe, absolutely necessary in 

 the production of this light; for it seemed to continue very little lessened in its 

 colour or vigour, till more than a fourth part of its air was let in. I have often 

 observed the same, as to the light produced in the mercurial experiments, only 

 that its colour in these was always pale : and there being such a seeming con- 

 gruity of appearances in all the circumstances, with those made on the attrition 

 of glass without it, that one might with some probability conclude, that the 

 light produced proceeds from a quality in the glass, on such a friction or mo- 

 tion given it ; and not from the mercury, any other ways than as a proper body, 

 which falling or rubbing on the glass, produces the light. And what would 

 seem further to corroborate such a conclusion is, that some time ago I took a 

 mercurial barometer, and rubbed the upper or deserted part of the tube between 

 my fingers, and a light ensued, without the motion of the quicksilver. Yet, 

 for all this, the conclusion is doubtful, and there may be such a quality as light 

 in mercury, as well as in glass, or any other body, as seems probable from the 

 following experiment, made on purpose. I took a small quantity of quicksilver, 

 and put it into a gallipot, in which varnish had often been used, by which 

 means it had got a pretty thick lining of it ; the weather at that time was moist 



