The gravimeter and microbarograpli vere installed in a heated "building 

 at the campsite located 650m from the edge of the island. The second gravi- 

 meter was set up in the center of an adjacent ice floe separated from the 

 island by two pressure ridges. On 3 June 1961 the two gravimeters were read 

 simultaneously . 



h. LaCoste-Romberg Gravimeter #22 



This instrument was originally built for underwater gravity measure- 

 ments, thus, provision for reading it remotely had already been incorporated 

 in the gravimeter 's construction. It was, therefore, relatively simple to 

 modify the meter so that its output couLd be recorded on Est erline -Angus strip 

 charts. This was desirable for long automatic recordings of wave records — an 

 impossibility with the usual method of visual recording. 



The gravimeter was mounted on a pedestal that passed through a hole 

 in the floor of the building. The pedestal was frozen solidly into the ice 

 and was not in contact with the building. 



The sensitivity of the gravimeter could be adjusted between limits 

 sufficiently wide to keep large amplitude peaks on scale, while intervals of 

 low amplitude coiiLd easily be read. Sensitivity was varied by adjusting the 

 longitudinal level of the gravimeter. Sensitivity calibrations for all values 

 of leveling were made on solid land at Point Barrow, Alaska, prior to operation 

 on the ice. 



Varying the sensitivity to match wave conditions caused a variation 

 of the instrument's natiaral period and damping constant according to the follow- 

 ing eq.uations: 



h=(K)l/2d (3) 



T = {K)^^^Tq (k) 



where h = actual damping 



K = sensitivity in eyepiece divisions per dial division 



d = critical damping 



T = natural period (sec) 



«'a= 22.i)- sec (instrument constant) 



For the two sensitivities used in this work, the natural periods and damping 

 constants were T = 26,h sec, h = I.18 critical, and T = I8.6 sec, h = O.83 

 critical. Since both damping constants were greater than O.707 critical, the 

 problem of resonance was not encountered (Richter, 1958). The response, how- 

 ever, fell off 6db per octave below the instrument's natiiral period, resulting 

 in recording little energy with periods less than 10 seconds. The problem of 

 aliasing, therefore, was avoided since the period range of interest was 10 to 

 100 seconds. 



c. World-Wide Gravimeter #5 



This is a portable gravimeter used on the pack ice as the second element 

 of a 2-element array. The wave motion was read visually and recorded every 5 



