ON THE FACTS OP EARTHQUAKE PHjENOMENA. 



289 



Sharp's (the Observer's) Chronograph. 



Five revolutions made in all cases. 



// 

 5 revolutions made in 24<"50 

 24-70 

 24-75 

 24-80 

 25-00 

 25-00 

 24-95 

 25-00 

 25-00 



This gives an average of 5 revolutions made in 25"-025=l revolution in 



25"-025 > „ 5"-005 



=5"-005 ; 1 division of large dial therefore is = — - — =0"-4171 



0"-4171 

 = 1 revolution of small hand, and — — — =0"-0139I0=l division of small 



dial. 



By the new mode of rating, taking an interval =60" or beats of the clock, 

 the revolutions made were as follow : — 



Exp. 1 in 60" made 11 revolutions -t- 0-91 7 of one revolution of large hand. 



2 „ „ 11 „ +0-972 



3 „ „ 11 „ +0-980 



4 „ „ 12 „ +0-042 „ „ 



The mean of which is =11 revolutions +0-978 as that made in 60", which 



:5"-0092. 



would be 12 revolutions in 60"-1102, or one revolution in 



60"-lI02_ 

 12 



Taking now the mean of the first and second (or new) determinations, we 



have „ 



5-0050 



5-0092 



2)10-0142 



5-0071 =the time of one revolution of the 



5"*0071 

 large dial, and — — — =0"'41 743= time of 1 division of the large dial=l 



0"-41743 



revolution of the small, and therefore — - — =0"-013914=time of 1 di- 



30 



vision of the small dial. 



To recapitulate, therefore : the following are the ratings of the two chro- 

 nographs as used in the subsequent experiment of the 30th and 31st of Oc- 

 tober and 2nd of November 1849. 



One revolution of 

 large hand or dial. 



One division of large 

 dial = one revolution 

 of the small hand. 



One division of 

 small hand. 



Wheatstone's. 

 Sharp's 



1851. 



5-14286 

 5-0071 



0-42857 

 0-41743 



0-014206 



0-013914 



u 



