Open AccessOn the Interpretation of Pd
Author(s) -
Jeffreys Harold
Publication year - 1958
Publication title -
geophysical journal of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0016-8009
DOI - 10.1111/j.1365-246x.1958.tb00052.x
Subject(s) - cusp (singularity) , discontinuity (linguistics) , interpretation (philosophy) , quadratic equation , physics , position (finance) , mathematics , function (biology) , arrival time , quadratic form (statistics) , geometry , mathematical analysis , combinatorics , finance , computer science , economics , programming language , evolutionary biology , transport engineering , engineering , biology
Summary Lehmann's observations of a large phase about 21°, lying a few seconds after the first arrival Pr , are discussed on two extreme hypotheses. On the first the distance varies as a quadratic function of sin e , so that d Δ/ de vanishes at 21°, where there is a cusp in the time curve. The values of dt / d Δ for Pr and Pd are found to be such that there is no possible position for the nearer cusp. On the second, a cubic form for t is assumed up to 21° for Pd. Pr must enter between 17° and 18°. The Pd ray emerging at 21° must reach about 0.03 R below the Mohorovičić discontinuity. The times of Pr imply that at the transition there must be a considerable discontinuity of velocity gradient but only a small one of velocity. The nearer cusp would be near 15°, but as it lies less than a second after the first arrival it is probably undetectable.