VOL. LXXX.] PHILOSOPHICAL TRANSACTIONS. 70Q 



the acid is yet unsaturated. Marine acid and iron applied to luna cornea effect 

 the same reduction of the silver to a metallic state, even when there is more acid 

 than is sufficient for both metals. 



The explanation of these phenomena will be attempted in the subsequent papers 

 which I propose to present on this subject to the Society. 



XXL Determination of the Longitudes and Latitudes of some Remarkable Places 

 near the Severn, By Edward Pigott, Esq. p. 385. 



Difference of longitudes in time between Greenwich and Frampton-house, 

 deduced from observed meridian transits of the moon's limbs. There were 1 3 of 

 these observations, from all of which the medium is 14™ 32' for the difference of 

 long, between those two places. This method of determining terrestrial longi- 

 tudes Mr. P. had detailed in the Philos. Trans, vol. 7^, and still thinks it cannot 

 be too strongly recommended. The latitude of the same place, taken with an 

 18-inch quadrant made by Bird, by a medium of 7 observations, was 51° 24' 58'^ 

 The same as given by his father in the Philos. Trans, vol. 71, is 51° 25' V' ; the 

 mean of both he takes at 51° 25' O", for the latitude of the observatory at Framp- 

 ton-house. 



Having thus settled the position of the Observatory, Mr. P. next proceeds to 

 give the particulars of the trigonometrical operations. He measured the same 

 base 3 times by different methods, the results were 2046, 2042, 2042 feet. As 

 the view from its extremities was very confined, another base of 186l yards was 

 deduced from it, situated on the high lands that edge the Severn. From the ex- 

 tremities of this 2d base, all the angles were taken with a tolerably good theodo- 

 lite, on which 2' might be easily read off. The results here given are the dis- 

 tances from the various places to the western extremity of their base, their per- 

 pendicular distances to its meridian, and its distance from these perpendiculars* 



8S64 



5906 E 



6609 N 



St. Hilary's Church. 



