0. Hecker — Gravity Determinations at Sea. 391 



ters were determined by the Physikalisch-Technisehe Reichs- 

 anstalt for three thermometers only; for the other three 

 thermometers I determined the corrections myself. With the 

 help of these corrections, the corrections depending on the 

 height of the thermometer were determined, combining there- 

 with the total corrections given by the Institute for several 

 points. After I had returned from my cruise on the Indian 

 and the Pacific Oceans, Mr. Meissner undertook an entirely 

 new and most careful determination of the errors of calibra- 

 tion : — small depressions of the zero point are of no conse- 

 quence, as they give only a constant difference. (See page 83 

 of the before mentioned publication.) He obtained practically 

 the same results as obtained from the previous investigations. 

 That also shows the great precision of the two determinations. 

 All this is given in my work. 



Bauer says then (also in italics) : " The corrections for the 

 various barometers on a standard barometer for various barome- 

 tric heights were never determined." 



This shows clearly that he did not at all understaud the 

 method of procedure adopted by me, and which was the only 

 right one. This is also shown by the following remark : 

 " Another very important point introducing a source of error 

 not considered by Hecker is with regard to the possible errors 

 in the vapor-tension tables used to convert boiling-point tem- 

 peratures into corresponding atmospheric pressure." He did 

 not notice that I have referred the corrections for the capacity 

 of the barometers, by a special series of observations, to the 

 boiling thermometers. This is the reason why the above men- 

 tioned errors disappear, and the vapor-tension table of Wiebe 

 plays only the role of an interpolation-formula. All this seems 

 to show clearly, that he has not a clear idea of the difficulties 

 of the determination of absolute barometric heights. 



We now come to where Bauer speaks of the results of my 

 observations. As a rule in estimating the precision of obser- 

 vations, one compares them, if possible, with observations 

 made with instruments affording greater precision. That is 

 quite self-evident. 



As to the Pacific Ocean, which he treats especially, the result 

 is, that the agreement, between the determinations of gravity 

 made on board and those by the pendulum, can be considered 

 to be satisfactory within the mean errors. That is the case for 

 Auckland, as it was twice the case for Honolulu. Two obser- 

 vations made near San Francisco as well as the observations 

 near Yokohama show also in the mean the satisfactory agree- 

 ment with the value of gravity deduced from the pendulum 

 stations. Besides, for six places on the Pacific, at which 

 determinations of gravity were made on each of the two 



