On page 195 of the above article, there is an unfortunate erroneous statement made which has the effect of casting considerable doubt on the reliability of the statistics for mining geophysics expenditures published by the SEG prior to 1969. The erroneous statement to which I refer is “. . .in past years, mining costs were obtained by multiplying mining crew‐months by an assumed average cost per crew‐month.” W. C. Kellogg and myself were responsible for the compilation and reporting of the 1967 and 1968 SEG mining geophysics statistics, which were published in Geophysics in December 1968 and December 1969, respectively. On the questionnaire forms that were sent out for those years (and also for previous years), there were, in fact, blank columns appropriately labeled, in which expenditures were to be reported directly for ground and airborne surveys and research. Only in a few percent of the cases where the responding organization had for some reason omitted the costs were these calculated from professional man‐months or line‐miles of survey using averaged (not “assumed”) costs reported by other respondents. For example, the average costs for 1968 ground geophysical surveys appears on page 854 in the 1968 article (Geophysics, December 1969) as Table 3.
On an Erroneous Statement of the Occurrence of Natural Human Footprints in the Palæozoic Rocks
