clwtrouiagucts is first atloctcil, and simultaiiccusly another clnck is stopjicd. 

 Tlie band of paper then eontinues to run for 48 liours at the rate of 1 mm. per 

 second, and so serves to receive notices of tl>e o;-(ui-r(^n e of otlier disturbances 

 after the first. The time of the first contact is i);iven by the clcu'k which stops; 

 and the interval between tliat and sul)sec|Uent contacts is dcterniined by the 

 leiit^th of jiaper unrolled from the first to subsequent marks. An alternative 

 arranjijement for receiving the marks caused by the attraction of the armatures 

 consists of a clock with a ]>rojectino' arbor which carries three drums, one of 

 which rotates in 'H h., another in 1 li., and tlie tliird in noO seconds. One of 

 the armatures carries tlirec jtencils which write on the tlin'c (bums, and the 

 other carries one pencil which writes on the last drum only. 



For the reasons which have been already sufficiently indicated, it cannot be 

 said that I'almieri's apparatus can be trusted to mea.sure even the relative 

 " intensitv " of ditierent earthquakes. As a record inii; seismo.scope it acts ad mi- 

 vablv, rejiistering many sliuht eart]i(|Uakes whicli would fail to allect a less 

 .sensitive instrument. 



§ TO. Tiine-tiihers. 



Besides the apjiaratus of Palniieri, many arrangements have been contrived 

 by other ob.servers with the view of detcrnu'nino; the time of occurrence of an 

 earth()uake. Mo.tt of these act by stopping a dock, either by an electromagnet 

 in conjunction with a circuil-closing .seismo.scope, or by direct mechanical 

 action, as when a delicately supported mass is overthrown by the disturbance. 

 ,\ time-taker used by Mr. jNIilne has the advantage over any of these, that it 

 records the time without stopping the clock. The a])j)aratus is shown in fig. 42, 

 Plate XXI.* C is a clock with a central seconds hand. The hour, minute, and 

 .seconds hands (/;, m, and .«) stand forward from the face ; their extremities are 

 bent outwards and are ti])ped with pieces of cork smeared with oily ink. A light 

 wooden ring R, covered, on the side facing the clock, with a \-arnishcd jiaper dial 

 which is graduated to correspond with the divisions of the clock face, is carried 

 by a truck on wheels, whicl) can run forward and make the dial on 7? touch the 

 clock iiands. Tliis happen at the time of an eartlnjuake, MJien the electromagnet 

 M, wliieh is in circuit with an electric seisnioscope, allows the wheel P to be 

 released, and to be cari'ied round through half a revolution b}' the weight W. 

 The rotation of P causes tlic dial to be advanced and withdrawn, by means of 

 the connecting-rod A'. The clock is not sensibly afFected by the contact, which 

 leaves marks on the dial 1\ showing the position of the hands when it occurred. 



I'^'om the account of cartlujuakc motion given in Chapter V, it will be 

 obvious that the time recorded by this or any other time-taking instrument will 

 depend very largely on the delicacy of the seismosco])0 in connection with it. 

 Earthquake motions generally begin so feebly as to make tlie time of their occur- 



* Trans, of the Seismologiual Society of Japan, Vol. IV, p. 89. 



