504 PHILOSOPHICAL TRANSACTIONS. [aNNO J76O. 



except in two observations, in one of which it amounts to 3'\ and the other 

 to 4" : but these differ as much from the mean of the six other observations 

 made at the same season of the year. Thus, assuming a parallax, the observa- 

 tions will be found to agree as well with that supposition, as they do with 

 one another. But if the observations are considered in themselves without any 

 allowance for parallax, they will differ sensibly from one another : nor is this 

 difference to be found only in two observations, in which case it may easily be 

 attributed to the account of the unavoidable errors ; but five observations in 

 July opposed to two in December and January, make the zenith distances vary 

 8", in the direction which a parallax ought to produce. 



% Mr. M. is aware, that it may be objected, that two observations made in 

 the winter season in December and January, at one of the maxima of the 

 parallax, are too few to determine a point of such consequence, and readily 

 agrees that the argument is weakened in proportion to the paucity of the ob- 

 servations : but then, it should also be considered, that the observations made 

 in March and April concur with the rest in supporting the supposition of a 

 parallax; and, on the whole, the observations will perhaps be judged to af- 

 ford a sufficient presumption of the existence of a parallax, to encourage the 

 undertaking of a careful trial. 



LXXIX. Further Experiments in Electricity, By Mr. Benjamin fFilson, 



F. H. S, p. 896. 



Being provided with a large square of glass, polished on both sides and fixed 

 upright on one edge, Mr. W. placed, for a conductor, a slender piece of ivory, 

 about one foot long, having one end within -^ of an inch from the centre of 

 the glass : at the other end were suspended 2 small balls of pith, by threads 4 

 inches long. The ivory was supported horizontally by a stand made of baked 

 wood. When the glass was made a little warmer than the external air, his 

 finger rubbed that side which was furthest from, and opposite to, the ivory. 

 On which, the two sides of the glass were electrified plus, as were likewise the 

 balls ; which continued plus, even after they were removed from the glass into 

 any part of the room. That the fluid here flowed from the finger into the 

 glass he thinks may be inferred from the following experiment. 



A piece of silver, being fixed on a slender rod of prepared wood, he rub- 

 bed the same glass with it, as he had done before with the finger ; on which 

 the silver was electrified minus, and both sides of the glass, with the conduc- 

 tor and balls, plus. There are therefore, he thinks, certain circumstances un- 

 der which the electric fluid passes through glass ; he says in certain circum- 

 stances, because in others, for instance, the Leyden bottle, the fluid does not 



