494 ELECTRICITY. 



odd ways. If, instead of drawing the knob of the jar 

 over the surface of the glass, we only touch the surface 

 of it here and there with the knob of the jar, and then 

 project the mixed powders as before ; separate star-like 

 figures will be formed about those points. The stars, 

 however, are more defined where a single powder is pro- 

 jected. Their rays or ramifications sometimes are few 

 and strong ; at other times they are numerous and slen- 

 der ; and frequently they do not go quite round the points 

 which had been touched with the knob of the jar. 



(b) ' Repeat the preceding experiment with this va- 

 riation only ; viz. that now the Leyden phial be charged 

 negatively in the inside, and the appearance of the con- 

 figurations will be much different from the above describ- 

 ed, which was produced by positive electricity. In the 

 present, very few rays or branicles will be observed ; the 

 powders mostly disposing themselves in roundish spots, 

 and generally it will be found that a central spot of one 

 powder is surrounded by another powder of a different 

 color. 



' Instead of dragon's blood and gum arabic, powders 

 of other colors may be projected upon the pane of glass, 

 such as powdered Prussian blue, sulphur, vermilion, re- 

 sin, &c, and thus the colors of the configurations may 

 be varied. 



' These powders adhere to the glass rather slightly, so 

 as not to bear being touched ; yet, if a piece of paper be 

 gently laid on the painted side of the glass, without rub- 

 bing it, and the edge of the paper be pasted all round 

 the edge of the glass, the figures may be preserved with- 

 out injury. But a better method is, to lay another pane 

 of glass of the same size upon the former, and to fasten 

 them by pasting a slip of paper all round their edges. If 

 such powders as are used by enamellers be projected 

 upon glass or porcelain, and these be afterward exposed 

 to a proper degree of heat in an enameller's furnace, 

 the configurations will thereby be rendered indelible. 



(c) * Take a piece of common writing paper, hold it 

 very near the fire, so as to render it quite dry and very 

 hot ; lay it flat upon a dry marble slab or a very dry ta- 

 ble, and in that situation draw over it the knob a charg- 



