The Benjamin Franklin’s Fluid Theory
Benjamin Franklin (1750) imagined the electricity as a invisible fluid.
Franklin assured that if any body had more fluid than usual, it could have a positive charge, but if it had less fluid than normal it had negative charge. Based on that, the assumption that the electricity flows from the positive to the negative came out. This theory was easy to understand and it was accepted as correct. This theory agreed with the experiments that were carried out in the 18 and 19 centuries.
Everybody accepted the idea that charges flows from the positive to the negative (conventional flow) and it was accepted as the truth.
It emerged a large number of concepts and formulas based on the conventional flow of the current between years 1750 and 1897.
Later it was discovered that the flow of the current was not running from the positive to the negative, but from the negative to the poisitive. (We have to remember that the current is a flow of electrons, that are negatively charged)
However, since this current is a flow of electrons, we can say that it is a negative current. When this flow is running throughout the conductor, it leaves a hole which is traveling from the opposite way of the flow, then we say that this current is possitive. That explains the assumption made by Benjamin Franklin.
Therefore, the theory presented by Benjamin Franklin is not true, though it works as if it were true.