210 New Outlines of Chemical Philosophy, 



A stick of black sealing-wax is the best non-conductor of any 

 substance that I have examined, but it is far from being perfect. 

 It mav, however, be used with advantage in many electrical ex- 

 periments, though not in such as require f)erfect insulation. 



As a perfect insulating stand is a valuable part of an electrical 

 apparatus, and as all the materials just mentioned were found 

 to be conductors, I was induced to try what effect might be pro- 

 duced by combining glass and sealing-wax. 1 took a thermo- 

 meter tube nine inches long, and joined it to a glass foot, like 

 the foot of a wine-glass, with black sealing-wax. Upon the top 

 of this tube a stick of sealing-wax an inch and a half in length 

 and half an inch thick is fixed, having a circular piece of plate- 

 glass three inches in diameter fixed horizontally upon the top 

 of it. The upper surface of this glass is gilt with gold-leaf, and 

 upon its centre one end of a slip of Dutch leaf is fixed with gum 

 water. This ser\'es as an index or electroscope ; for, as soon as 

 the gilt surface of the glass cap is charged, this index stands 

 erect, being repelled equally on every side by the charged sur- 

 face of the cap. 



The perfection of this stand, as a iKjn-conductor, was proved 

 thus: 



The wire upon the top of one of my best electrometers was 

 applied to the glass foot of the stand, and then to the thermo- 

 meter tube fixed upon it, without the least effect being produced 

 upon the Dutch leaves : but as soon as the electrometer was brought 

 near the cap the leaves began to diverge ; and on coming into 

 contact, either with the under or upper side of it, the leaves in- 

 stantlv diverged to an angle of 90 degrees or more, according 

 to the height of the charge which the cap had received. 



In my fifth experiment, (Phil. Mag.vol.xliii. page 430,) which 

 vvas made to prove the permeal)ility of glass by the electrical 

 elements, the neck of a Florence flask was closed with an ani- 

 mal substance communicating with the earth, by which means 

 no electricity could enter the flask without passing through the 

 glass. 



The truth of this conclusion may be evinced by means of the 

 following experiment, 



Exp. 10. — 1 took the same flask mentioned in the fifth ex- 

 periment, and after having removed the animal membrane from 

 it, I dipped the top of its neck and stopper into melted sealing- 

 wax, by which means the neck of the flask was closed more com- 

 pletely/ than if it had been hermetically sealed; for it has been 

 proved in the preceding experiments, that sealing-wax is a much 

 worse conductor tha i glass. 



An excited barometer tube being held over the top of the 

 neck of the flask at a short distance, no effect was produced in 



the 



