elOs 
Gravity Observations 
A Frost-type grevimeter from the University of “Wisconsin was 
operated on Station Alpha. During much of its operation et this station, 
the motion proved erratic anc gravity readings proved difficult. The motion 
of the floe wes often sufficient to cause the boom to swing against the 
stops. Despite this, many readiness were made. Ties proved another difficulty. 
Ties to known gravity points were made when a Worden high-range gravity 
meter was brought in by someone from the University of Wisconsin. The data 
was unfortunately left untied at the end of the station occupation since 
the evacuation was too rapid to permit a tie. 
The gravimeter at Alpha was read, whenever possible, for a period 
of five minutes et three-seconc intervals. These readings showed the long= 
period motion (20 to O second period) that had been observed previously 
by Crary. This wave motion has been examined in some detail and several 
records were analyzed by Fourier's method. It is believed that these waves 
are associated with the group and phase velocity minimum lying between 
the branches of the dispersion curve associased with gravity waves and with 
flexural waves for an ice-covered ocean. Calculations of the entire long- 
period dispersion curve for the Arctic Ocean situation have been mace and 
the velocity minimum occurs in the range of observed periods. It might be 
expected that laree amplitudes would be found at this minimum. Clear proof 
that these are traveling waves is lackin>, elthough it seems hiehly likely 
that this is the case. A tripartits array of gravimeters or lone=-neriod 
selismozraphs would settle this question and allow determination of phase 
velocities and directional spectra if they are, indeed, traveling waves. 
TE. STUDY OF THE STRUCTURE AN™ CHARACTERISTICS OF SHA ICE 
Seismic methods were used to investigate surface waves of various 
