B. TERRESTRIAL PHYSICS AND METEOROLOGY. 93 



pecially studied by Hochstetter, who has collected the ma- 

 terial therefor with great patience. The earthquake wave 

 that spread from Peru westward was recorded at Sydney, 

 Australia, by the self-registering tide-gauge, and the record 

 shows that, while during five days the ocean went through 

 its regular changes, there occurred on the 13th of August, in 

 the afternoon, a series of vibrations corresponding to the so- 

 called earthquake Avave. Hochstetter and Schmick deduce 

 the following conclusions from their study of the record at 

 Sydney, Australia: 



1. In reference to the earthquake itself, that it must have 

 affected a circular region almost entirely under the sea. 



2. The lunisolar tidal wave, as well as the sea wave of the 

 earthquake, require twenty hours and thirty-seven minutes 

 in order to pass over the distance from Arica to Sydney, both 

 species of waves having precisely the same velocity. 



3. The notion that has previously obtained, viz., that only 

 the southern portion of the great Pacific Ocean is subject to 

 primary waves that spread themselves over the entire earth 

 in two or three days, is quite false. 



Having subsequently obtained from Russell, the director of 

 the observatory at Sydney, a complete copy of the record for 

 the entire year 1871, Schmick has been able by the study of 

 this material to establish the following propositions : 



1. The tide records agree precisely with the Newtonian 

 theory of gravitation. 



2. That the known laws peculiar to harbors, known as the 

 establishment of the port, hold as well for Australia as for 

 Europe. 



3. That an observation made by Captain Cook, viz., that 

 on the Australian coasts in the summer time the night tide 

 is the highest, while in winter the day tide is the highest, 

 and which observation has been for a long time doubted, be- 

 cause the opposite rule holds for Europe, is, however, quite 

 correct. The difference between the tides in Europe and 

 those on the Australian coast consists chiefly in the fact 

 that the latter are very much affected by the tide waves re- 

 flected back to Australia from the western coast of South 

 America. 



4. These reflected tidal waves occupy twenty hours and 

 thirty-four minutes in passing from South America to Sydney. 



