35 



100. Duplex pendulum seismograph, designed by 

 Prof. J. A. Swing. 



Made ~by the Cambridge Scientific Instrument Company. 

 E. 143. 1888. 



This is an instrument for registering on a fixed plate of 

 smoked glass, with suitable magnification, the whole horizontal 

 motion of the ground. It consists of a vertical case, supported 

 on three levelling screws. On the centre of the base stands an 

 inverted pendulum pivotted in a hard steel cup. The bob of 

 the pendulum is a massive disc. This, though free to move 

 about the base in all directions, is kept vertical, and in nearly 

 neutral equilibrium, by being geared by a ball and socket joint 

 to another somewhat larger massive disc which hangs by three 

 parallel wires from the top of the box. Any horizontal motion 

 of the base is thus communicated to the upper disc. The 

 motion of this disc is recorded by means of a vertical rod which 

 is supported by agimbal joint fixed on a side bracket, which acts 

 as the fulcrum of a lever ; the lower and shorter end of the rod 

 works in the disc by a ball and socket joint, while the upper and 

 longer end carries a horizontal pointer at its extremity, which 

 traces a multiplied record of the motion on a fixed horizontal 

 plate projecting from the case. The degree of stability of the 

 combination is adjusted by raising or lowering the upper disc. 



101. Model showing the motion of an earth particle 

 during the earthquake of January 15, 1887. 



By Prof. S. SeJciya, Imperial University, ToJcio, Japan. 

 E. 11. 1889. 



This consists of a length of red coloured wire twisted about, 

 and divided into three parts. The course taken by the wire 

 represents the path pursued by an earth particle during the 

 above earthquake as determined by the records of horizontal 

 and vertical seismographs. The actual motion of the ground, 

 both horizontal and vertical, is magnified 50 times. The model 

 is made in three parts for convenience, and on it are placed 

 consecutive numbers, from 1 to 72, to indicate the position of 

 the particle at the end of the corresponding second. 



For a description of this model and its mode of construction, 

 see Journal of the College of Science, Imperial University of 

 Japan, Vol. I. 



102. Seismic apparatus to give the time and direction 

 of an earthquake shock. 



Made by Brassart Bros., Central Meteorological Office, 

 E. 10 to 12. 1884. Home. 



This consists of an oblong stand with levelling screws. On 

 one end stands a ball on the top of a rod lightly balanced, and 

 standing within a hollow octagon marked with compass points 



