238 Royal Institution :— 
8000 feet, are here wanting. But as the junction of the Carboni- 
ferous Limestone with the Lower Old Red is traced towards the east, 
the thickness of strata between the two formations gradually in- 
creases, until at the Pentland Hills the whole of the Lower Carboni- 
ferous series and a considerable part of the Upper Old Red have come 
in; and these strata, as at Lesmahagow, rest quite unconformably on 
the base of the Lower Old Red Sandstone and the higher beds of 
the Upper Silurian. Hence it becomes apparent that in the south 
of Scotland, as in Ireland, there is a great physical break between 
the Upper Old Red Sandstone and the lower part of that for- 
mation. 
The author next pointed out the character of the Upper Old Red 
Sandstone in East Lothian and Berwickshire ; showing that it 
graduated by imperceptible stages into the Lower Carboniferous 
sandstones, and formed with these one great lithological series. 
The former wide extension of the Upper Old Red Sandstone 
throughout the south-east of Scotland was shown by the height at 
which it occurs among the Lammermuirs. These hills must un- 
questionably have been covered by it; and hence the denudation of 
the south of Scotland will eventually be shown to be one of the greatest 
which this country has undergone. The author concluded by 
sketching the physical geography of South Scotland during the 
Upper Old Red Sandstone period, in so far as it was indicated by 
the facts presented in this paper. He showed that the rate of 
subsidence was probably much greater in the eastern than in the 
western districts, inasmuch as the whole of the vast series of Upper 
Old Red and Lower Carboniferous sandstones had accumulated in 
the Lothians and Berwickshire before the base of the Lesmahagow 
hills began to be washed by the waves of the encroaching sea. 
ROYAL INSTITUTION OF GREAT BRITAIN. 
January 20, 1860.— On the Influence of Magnetic Force on the 
Electric Discharge.” By John Tyndall, Esq., F.R.S. 
The intention of the speaker was to bring before the meeting a 
series of experiments illustrative of the constitution of the electric 
discharge and of the action of magnetism upon it. The substance 
of the discourse was derived from the researches of various philo- 
sophers, its form being regulated to suit the requirements of the 
audience. 
1. The influence of the transport of particles was first shown by 
an experiment suggested, it was believed, by Sir John Herschel, and 
performed by Professor Daniell. The carbon terminals of a battery 
of 40 cells of Grove were brought within one-eighth of an inch of 
each other, and the spark from a Leyden jar was sent across this 
space. This spark bridged with carbon particles the gap which 
had previously existed in the circuit, and the brilliant electric 
light due to the passage of the battery current was immediately 
displayed. 
