L. A. Bauer — Ocean Gravity Observations. 245 



Art. XXIII. — Hecker's Remarks on Ocean Gravity Obser- 

 vations ; by L. A. Bauer. 



It is frequently suggested by persons, presumably familiar 

 with previous work, that it would be desirable to include gravity 

 observations on the Carnegie. We are told that ocean gravity 

 work, of requisite accuracy, is one of the few remaining heroic 

 problems. Before deciding on any additional work a careful 

 survey is made of existing knowledge and of the actual require- 

 ments for obtaining trustworthy data. I was thus led into an 

 examination of past ocean gravity work, viz., that by Dr. 

 Hecker on three cruises between 1901-09, under the auspices 

 of the International Geodetic Association and published in 

 three monographs aggregating 500 quarto pages. Examina- 

 tion was made at first only in general ; however, I soon became 

 engaged in an exhaustive examination of the entire problem, 

 not only going this time more deeply into Hecker's methods of 

 observation and of computation, but also consulting experts in 

 thermometry and barometry of the U. S. Bureau of Standards 

 and of the G. S. Weather Bureau, besides well-known geod- 

 esists and physicists. The final result of this preparatory study 

 was the paper " On Gravity Determinations at Sea" published 

 in this Journal, January, 1911. This paper received the en- 

 dorsement of several well-known investigators to whom the 

 manuscript was submitted before publication. Its special aim 

 was to arouse general interest in this difficult subject and to 

 assist in making clear the direction in which further advance 

 was necessary. Returning December 24 from a cruise of the 

 Carnegie, I found that Dr. Hecker had made reply to some points 

 in my paper. His remarks were originally published in the 

 journal of which he is chief editor (Gerland's Beitrage zur 

 Geophysik, Bd. xi, Heft 1, June, 1911, p. 200); in Novem- 

 ber a modified translation appeared in this Journal. Refer- 

 ences throughout this article will be to this translation. 



I must begin by correcting some of Hecker's statements. 

 He infers that we have introduced for gravity work on the 

 Carnegie an inferior method of reading the boiling-point ther- 

 mometer, viz., with a hand lens instead of a telescope, as he had 

 done. I had stated explicitly (I. <?., p. 4) that the boiling-point 

 observations on the Carnegie were not made for the purpose of 

 gravity determinations ; " the prime purpose being to obtain 

 data for controlling the corrections of our aneroids, the instru- 

 mental equipment was in accordance with this aim." This was 

 on our first cruise ; on the present cruise we have replaced the 

 hand lens by a telescope, but we are not yet willing to regard 

 our individual results as gravity determinations. 



