CONVECTION, OR CARRYING DISCHARGE — FLUID TERMINATIONS OR DROPS. 149 



1590. When a ball is covered with a thick conducting fluid, as treacle or syrup, it 

 is easy by inductive action to determine the wind from almost any part of it (1577-) ; 

 the experiment, which before was of rather difficult performance, being rendered facile 

 in consequence of the fluid enabling that part, which at first was feeble in its action, 

 to rise into an exalted condition by assuming a pointed form. 



1591. To produce the current, the electric intensity must rise and continue at one 

 spot, namely, at the origin of the current, higher than elsewhere, and then, air having 

 a uniform and ready access, the current is produced. If no current be allowed (1574.), 

 then discharge may take place by brush or spark. But whether it be by brush or 

 spark, or wind, it seems very probable that the initial intensity or tension at which a 

 particle of a given gaseous dielectric charges, or commences discharge, is, under the 

 conditions before expressed, always the same (1410.). 



1592. It is not supposed that all the air which enters into motion is electrified ; on 

 the contrary, much that is not charged is carried on into the stream. The part which 

 is really charged may be but a small proportion of that which is ultimately set in mo- 

 tion (1442.). 



1593. When a drop of gum water (1584.) is made negative, it presents a larger 

 cone than when made positive; less of the fluid is thrown off*, and yet, when a ball is 

 approached, sparks can hardly be obtained, so pointed is the cone, and so free the 

 discharge. A point held opposite to it did not cause the retraction of the cone to 

 such an extent as when it was positive. All the effects are so different from those 

 presented by the positive cone, that I have no doubt such drops would present a very 

 instructive method of investigating the diff*erence of positive and negative discharge 

 in air and other dielectrics (1480. 1501.). 



1594. That I may not be misunderstood (1587.), I must observe here that I do 

 not consider the cones produced as the result only of the current of air or other 

 insulating dielectric over their surface. When the drop is of badly conducting matter, 

 a part of the effect is due to the electrified state of the particles, and this part consti- 

 tutes almost the whole when the matter is sealing-wax, oil of turpentine, and similar 

 insulating bodies (1588.). But even when the drop is of good conducting matter, as 

 water, solutions, or mercury, though the effect above spoken of will then be insensible 

 I6O7.), still it is not the mere current of air or other dielectric which produces all the 

 change of form; for a part is due to those attractive forces by which the charged drop, 

 if free to move, would travel along the line of strongest induction, and not being free 

 to move, has its form elongated until the sum of the different forces tending to pro- 

 duce this forin is balanced by the cohesive attraction of the fluid. The effect of the 

 attractive forces are well shown when treacle, gum water, or syrup is used ; for the 

 long threads which spin out, at the same time that they form the axes of the currents 

 of air, which may still be considered as determined at their points, are like flexible 

 conductors, and show by their directions in what way the attractive forces draw 

 them. 



