VOL. XXXVIII.J l»HILOSOPHICAL TltANSACTION'S. ()3g 



near tliem, they immediately became electrical. He made this experiment with 

 ice, with a lighted wood-coal, and with every thing that came into his mind ; 

 and he constantly remarked, that such bodies as of themselves were least 

 electrical, had the greatest degree of electricity communicated to them at the 

 approach of the glass tube. 



3. Mr. Gray says, Phil. Trans. N° 417, that bodies attract more or less ac- 

 cording to their colours. This led M. Du Fay to make several very singular 

 experiments. He took Q silk ribbons of equal size, one white, one black, and 

 the other 7 of the 7 primitive colours^ and having hung them all in order on 

 the same line, and then bringing the tube near them, the black one was first 

 attracted, the white one next, and the others in order successively to the red 

 one, which was attracted least, and the last of all. He afterwards cut out Q 

 square pieces of gause, of the same colours with the ribbons, and having put 

 them one after another on a hoop of wood, with leaf-gold under them, the 

 leaf-gold was attracted through all the coloured pieces of gause, but not through 

 the white or black. This inclined him at first to think, that the colours con- 

 tributed much to electricity. But 3 experiments convinced him of the con- 

 trary : the first, that by warming the pieces of gause, neither the black nor 

 white pieces obstructed the action of the electrical tube more than those of the 

 other colours. In like manner, the ribbons being warmed, the black and white 

 are not more strongly attracted than the rest. The second is, the gauses and 

 ribbons being wetted, the ribbons are all attracted equally, and all the pieces of 

 gause equally intercept the action of electric bodies. The third is, that the 

 colours of a prism being thrown on a piece of white gause, there appear no 

 differences of attraction. Whence it follows, that this difference proceeds not 

 from the colour, as a colour, but from the substances that are employed in the 

 dying. For when he coloured ribbons, by rubbing them with charcoal, car- 

 mine, and such other substances, the differences no longer proved the same. 



4. Having communicated the electricity of the tube by means of a pack- 

 thread, after Mr. Gray's manner, he observed, that the experiment succeeded 

 the better for wetting the line ; and that it may be supported on glass-tubes in- 

 stead of silk-lines. And he made this experiment at J25S feet distance, in a 

 garden, though the wind was high, and though the line made 8 returns, and 

 passed through two different walks. By means of two silk loops he adjusted 

 two lines in such a manner, that their ends were but a foot distance from each 

 other, and he remarked that the electric virtue was still communicated. He 

 has since that seen, in the Philos. Trans. N° 426, that Mr. Gray had the same 

 thought, and that he had done the same with rods. This experiment put him 

 on placing several different bodies between the two lines, to examine which di- 

 minished or intercepted the electricity, and which gave no obstruction to it. 



