MAKE A MEME View Large Image The Quarterly journal of the Geological Society of London (13204971914).jpg 222 T GRAY ON A SEISMOGRAPHTC APPARATUS <br> Fig 4 ” Diagram of Continuous-motion Governor <br> Magazine' Nov 1881 p 358 to close an electric circuit which ac- <br> ...
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Keywords: The Quarterly journal of the Geological Society of London (13204971914).jpg 222 T GRAY ON A SEISMOGRAPHTC APPARATUS <br> Fig 4 ” Diagram of Continuous-motion Governor <br> Magazine' Nov 1881 p 358 to close an electric circuit which ac- <br> tuating electromagnets causes a mark to be made on the drum 1 <br> and at the same time the dial of the time- keeper T to move suddenly <br> forward against ink-pads fixed to the ends of the hands In this <br> way the hour minute and second at which the mark was made on <br> the drum D is recorded ; and this combined with the record of the <br> motion which is being written on the drum is sufficient to determine <br> the time at which any particularly prominent feature of the shock <br> took place <br> The instruments just described have been made to suit the earth- <br> quakes which are commonly experienced in Japan and are conse- <br> quently not adapted for use where the displacement of the earth is <br> great A similar set of apparatus could however be made to record <br> earthquakes of considerable magnitude The utility of having such <br> records of earthquakes will be readily admitted ; and I should call <br> special attention to the great value of the combination of the record <br> of the time of the occurrence with that of the motions When the <br> time of occurrence of any of the chief features of the shock is known <br> for a number of places it becomes a comparatively easy problem to <br> determine the origin of the shock and its rate of propagation It has <br> been the usual practice in earthquake-observations to take an approx- <br> imate measurement of the magnitude and direction of the movement <br> at any place and to deduce angles of emergence and direction of pro- <br> pagation Now it is hardly necessary to point out that the direction <br> of movement at any point is very much influenced by the presence <br> or absence of surface undulations and of refractions and reflections <br> from strata of different elastic moduli I am of opinion that the 36928819 113681 51125 Page 222 Text 39 http //www biodiversitylibrary org/page/36928819 1883 Geological Society of London Biodiversity Heritage Library The Quarterly journal of the Geological Society of London v 39 1883 Geology Periodicals Smithsonian Libraries bhl page 36928819 dc identifier http //biodiversitylibrary org/page/36928819 smithsonian libraries Information field Flickr posted date ISOdate 2014-03-16 Check categories 2015 August 26 CC-BY-2 0 BioDivLibrary https //flickr com/photos/61021753 N02/13204971914 2015-08-26 13 53 52 cc-by-2 0 PD-old-70-1923 The Quarterly journal of the Geological Society of London 1883 Photos uploaded from Flickr by FĂŚ using a script
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