VOL. XLV.] PHILOSOPHICAL TRANSACTIONS. 441 



spoken of is formed through them the most readily. Water Ukewise is an ex- 

 cellent conductor ; for the electrical power makes no difference between solids 

 and fluids as such, but only as they are non-electric matter. 



Mons. le Monnier the younger at Paris, in an account transmitted to the 

 Royal Society, takes notice of his feeling the stroke of the electrified phial along 

 the water of two of the basins of the Thuilleries, the surface of one of which 

 is about an acre, by means of an iron chain which lay on the ground, and was 

 stretched round half their circumference. On these considerations it was con- 

 jectured, as no circuit had as yet been found large enough so to dissipate the 

 electrical power as not to make it perceptible, that if the non-electrical con- 

 ductors were properly disposed, an observer might be made sensible of the elec- 

 trical commotion quite across the river Thames, by the communication of no 

 other medium than the water of that river. In any other part of natural philo- 

 sophy, as we should draw conclusions only from the facts themselves, it was deter- 

 mined to make the experiment. 



The making this experiment drew on many others, and as the gentlemen con- 

 cerned flatter themselves that they were made with some degree of attention and 

 accuracy, they thought it not improper to lay a detail of all the operations be- 

 fore the Royal Society. To try this experiment, it was absolutely necessary that 

 a line of non-electric matter, equal in length to the breadth of the river, should 

 be laid over it, so as not to touch the water in any part of its length; and the 

 bridge at Westminster was thought the most proper for that purpose, where the 

 water from shore to shore was somewhat more than 400 yards. 



Accordingly on July 14, 1747, several members of the Royal Society met to 

 assist in making the experiment. A line of wire was laid along the bridge, not 

 only through its whole length, but likewise turning at the abutments, reached 

 down the stone steps on each side of the river low enough for an observer to dip 

 into the water an iron rod held in his hand. One of the company then stood on 

 the steps of the Westminster shore, holding this wire in his left hand, and an 

 iron rod touching the water in his right; on the steps facing the former on the 

 Surry shore, another of the company took hold of the wire with his right hand, 

 and grasped with his left a large phial almost filled with filings of iron, coated 

 with sheet-lead, and highly electrified by a glass globe properly disposed in a 

 neighbouring house. A third observer standing near the second dipped an iron 

 rod held in his left hand into the water, and touching the iron hook of the 

 charged phial with a finger of his right hand, the electricity snapped, and its 

 commotion was felt by all the three observers, but much more by those on the 

 Surry shore. The third obser\'er here was no otherwise necessary, than that the 

 river being full, the iron was not long enough to be fixed in the mud on the 

 ghore, and therefore was in want of some support. The experiment was repeated 



VOL. IX. 3 L 



