246 L. A. Bauer — Ocean Gravity Observations. 



The experts consulted agreed that it would not be safe to 

 rely exclusively upon barometers, as did Hecker, damped to 

 such a degree that, as he confesses, observations made with them 

 at sea, under supposedly ideal conditions, were not of the 

 desired accuracy. Thus he says (I. c, p. 390), " this, of course, 

 cannot be otherwise, for, as is well known, highly clamped 

 barometers, when perfectly at rest, do not have \ery accurate 

 readings." As the final outcome of all conferences and expe- 

 riences, the conclusion has been reached that it will not be 

 worth while to take up gravity work seriously on the Carnegie 

 unless substantial improvements can be made upon the boiling- 

 point-barometer method ; we are continuing, however, with 

 our present equipment, the necessary observations for the con- 

 trol of our aneroids. I shall have to postpone for some future 

 occasion the report upon this feature of our work.* 



In spite of all care bestowed, the possibilities of appreciable 

 errors are so numerous as to raise the question whether grav- 

 ity data obtained by Hecker's method would yield individual 

 results of requisite accuracy. These errors in themselves 

 appear trivial until converted into gravitational quantities. 

 Thus, for example, an error in the boiling-point temperature 

 of but 0°-001 C. corresponds to about 0*035 cm or 1/28000 part 

 of g, the order of accuracy required, I am informed, to meet 

 modern requirements. It may be that Hecker considers that 

 he has reached this accuracy. As the result of my exami- 

 nation I was led to the conclusion (I.e., p. 161) that "it will 

 not be surprising if it be found that many of the most recently 

 published results are in error by an amount approximating to 

 0*l cra , or about 1/10000 part of g." 



Hecker questions my statement regarding his thermometer 

 corrections. The facts as derived from his three publications 

 are as follows (pp. 6-7, 1903 ; pp. 81-83, 1906, and pp. 39-40, 

 1910). The total corrections of thermometers employed in the 

 Atlantic cruise of 1901, the Indian and Pacific Ocean cruise of 

 1904-05, and in the Black Sea work of 1909, were determined 

 but once, viz., before starting out in 1901. If I understand 

 him rightly, only the corrections dependent upon inequal- 

 ities of bore of tube (the calibration corrections) were deter- 

 mined a second time, namely, at the end of the work in 1904-5. 

 All other corrections, however, e. g., those dependent upon the 

 zero, the fundamental interval, reduction to standard scale, etc , 



* Hecker is correct with regard to the impossibility of reading successive 

 high and low phases of the barometers used on the Carnegie ; 1 had misin- 

 terpreted the observer's notes. However, since then we have made some 

 preliminary experiments in which successive high and low readings were 

 obtained by using a hand magnifier and estimating the readings, as closely 

 as possible, with the eye and attempting to secure the requisite accuracy by 

 multiplying the observations under varied conditions on the principle suc- 

 cessfully used in our magnetic work. 



