Reports and Proceedings— Geological Society of London. 237 
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GrontogicaL Society oF Lonpon. 
I.—March 7, 1883.—J. W. Hulke, Esq., F.R.S., President, in 
the Chair.—The following communications were read :— 
1. “On Gray and Milne’s Seismographic Apparatus.” By Thomas 
Gray, Esq., B.Sc., F.R.S.E. Communicated by the President. 
This apparatus was stated to have for its object the registration 
of the time of occurrence, the duration, and the nature, magnitude 
and period of the motions of the earth during an earthquake. The 
instrument was made by Mr. James White, Glasgow, and is to be 
used by Prof. John Milne in his investigations in Japan. 
In this apparatus two mutually rectangular components of the 
horizontal motion of the earth are recorded on a sheet of smoked 
paper wound round a drum, kept continuously in motion by clock- 
work, by means of two conical pendulum-seismographs. The vertical 
motion is recorded on the same sheet of paper by means of a com- 
pensated-spring seismograph. In details these instruments differ 
considerably from those described in the Philosophical Magazine for 
September, 1881, but the principle is the same. 
The time of occurrence of an earthquake is determined by causing 
the circuit of two electromagnets to be closed by the shaking. One 
of these magnets relieves a mechanism, forming part of a time- 
keeper, which causes the dial of the timepiece to come suddenly 
forward on the hands and then move back to its original position. 
The hands are provided with ink-pads, which mark their positions 
on the dial, thus indicating the hour, minute, and second when the 
circuit was closed. The second electromagnet causes a pointer to 
make a mark on the paper receiving the record of the motion. 
This mark indicates the part of the earthquake at which the circuit 
was closed. 
The duration of the earthquake is estimated from the length of 
the record on the smoked paper and the rate of motion of the drum. 
The nature and period of the different movements are obtained from 
the curves drawn on the paper. 
2. “Notes on some Fossils, chiefly Mollusca, from the Inferior 
Oolite.” By the Rev. G. F. Whidborne, M.A., F.G.S. 
The fossils described by the author are, with the exception of some 
in the British Museum and a few of his own collecting, in the 
collections from the Inferior Oolite which enrich the Bristol Museum. 
Several of the species are new; of these there are Ostrea 2, Gry- 
phea 3, Hxogyra 1, Pecten4, Harpax 1, Plicatula 1, Placuna 1, Ger- 
villia 3, Pinna 2, Lima 11, Mytilus 2, Arca 3, Nucula 1, Cardium 2, 
Cypricardia 1, Myoconcha 2, Astarte 1, Opis 1, Thracia 1, Pholadomya 
3, Myacites 1, and Terebratula 2, besides one or two more that are 
doubtful. 
8. “On some Fossil Sponges from the Inferior Oolite.” By Prof. 
W. J. Sollas, M.A., F.G.S. 
Some fossil Sponges have been described from the Inferior Oolite 
