these occasions have been from 300 to 800 times ; sometimes one, 

 and sometimes another being used, according to the states of the air 

 or moon, or other circumstances. 



The observations here recorded, were made principally from the 

 year 1787 to 1798 inclusive, and they are given in the order in which 

 they occurred with all the phenomena noticed each time, and notes 

 of correction added from subsequent observations respecting stars 

 mistaken for satellites, or satellites wrongly numbered. For Dr. Her- 

 schel always added a configuration to his descriptions, in order to avoid 

 mistakes, and in general made, by previous estimate, a sketch of the 

 places where known satellites might be expected ; some misconcep- 

 tions were unavoidable, in consequence of the interruptions to his 

 observations from cloudy or moon-light nights, as well as from small 

 stars that unexpectedly interfered. 



From all the observations thus made, and from accurate measures 

 taken by different micrometers, the author infers the nodes of the 

 two first satellites to have nearly the same longitude of 165^; that 

 their inclination is also the same, 78 58' ; and the motion of both, 

 from their ascending node to the greatest elongation, retrograde. 

 The periodic time of the first is found to be 8 d 16" 56 m 5 s ; and that 

 of the second 13 d ll h 8 m 19 9 ; their distances at greatest elongation 

 36" and 48" respectively. 



To these determinations respecting the orbits of the satellites, 

 Dr. Herschel adds his estimate of the distances to which they must 

 move from the body of the planet before they become visible by his 

 20-feet telescope. The first requires to be at more than half its 

 greatest elongation. The second also becomes invisible when it is 

 within half its greatest elongation. If there be an interior satellite, 

 as large as the first, he imagines it would be visible through so small 

 a part of its orbit, as not to be seen for two nights together. 



Notwithstanding this difficulty, the author thinks he has seen an 

 interior satellite. And with regard to exterior satellites, though 

 nothing has been correctly ascertained, the number and positions of 

 different objects recorded is such, that the author enumerates as far 

 as a supposed sixth satellite. 



An Account of some Experiments with a large Voltaic Battery. By 

 J. G. Children, Esq. F.R.S. Read June 15, 1815. [Phil. Trans. 

 1815, p. 363.] 



The battery with which these experiments were made, has 21 

 cells, each containing about 40 gallons of water, to which was added 

 a mixture of nitric and sulphuric acids, at various intervals, beginning 

 with -^o-th, and ending with ^Vth part of the water. Into each cell 

 was immersed a zinc plate, with a pair of copper plates, one on each 

 side, but connected together at the bottom, and also duly connected 

 to the zinc in the cell adjacent. Each plate had 16 square feet of 

 surface. 



The first series of experiments were on the comparative liability of 



