ON SEISMOLOGICAL INVESTIGATIONS. 



63 



Under the lieadin,2; ' Calculated ' are given tlie daily travels for the 

 temperature change calculated with the coefficients 111 mm. and 4-0 mm. 

 for 1° as found above from the diurnal inequalities. The M.-B. machine 

 shows only about half the calculated travel ; the M.-S. machine no sensible 

 travel at " all. It should be mentioned that the zero of the latter is 

 adjusted every morning, but this does not affect the above figures, which 

 are deduced (partly by estimation) from the undisturbed daily traces. 



A test experiment "was made on .July 29 as follows : 



At 10 a.m. a stove was lit in the Observatory in order to cause a 

 rapid rise of temperature. 



At 12.30 p m. the stove was removed and a large block of ice was 

 introduced in order to caiise a sudden fall. 



65 



60' 



55 



SCALE 

 FOR MB 



MM 

 100 



50 



SCALE 



FORMS 



200 



300 



NOON I5-0 140 I5'0 160 170 



Temperature Experiment at Shide, July 29, 191-5. 



The readings of the thermograph and the corresponding wanderings 

 of the two machines are shown in the diagram. It will be seen : — 



(a) That neither machine responds to the rise of temperature in any- 

 thing like the degree suggested by the diurnal coefficients. The total 

 rise of temperature is over 10°, and we should expect deflections of 177 mm. 

 and 40 mm. respectively ; instead of which we get about 19 mm. and 

 11 mm. 



