The thickness of the Athabaska Glacier has been obtained along eight transverse profiles by an investigation of gravity anomalies. Three-dimensional computations with a low-speed digital computer were made in this study to acquire more precise results than previously obtained. The thickness of the glacier varies front 326 m. on a line below the lower ice fall to 49 m. near the terminus. The accuracy of the results is discussed and compared with independent data from bore holes and a seismic program. The cross-section of the glacier valley was found to approximate a parabola on several lines. From a knowledge of the thickness. shape and surface slope of the glacier, the average shear stress exerted by the bed on the ice was found to be 1.0 bar.

Compared with freshwater ice, whose physical properties are well known, sea iceis a relatively complex substance whose transition to a completely solid mixtureof pure ice and solid salts is completed only at extremely low temperaturesrarely encountered in nature. The physical properties of sea ice are thusstrongly dependent on salinity, temperature and time. Many of these propertiesare still not fully understood or accurately known, particularly those importantfor the understanding of a natural ice cover. The specific heat for example isan important term in the calculation of the heat energy content of a cover.However, Malmgren (1927), whose calculatedvalues of the specific heat of sea ice are in general use, neglected the directcontribution of the brine present in inclusions. Re-examination of thequestion of specific and latent heats of sea ice has led to distinguishingbetween the freezing and melting points and enabled significant observations inthis range. Similarly, because the thermal conductivity is a necessary parameterin the description of the thermal behaviour of ice. the sea-ice modelsuggested by Anderson (1958) has beenmodified and extended in the present work to the case of saline ice containingair bubbles. This enabled the completion of calculations of density andconductivity. In order to illustrate the theoretically calculated values.measurements were made on sea-ice samples to determine the specific heat,density and thermal conductivity.

In August 1961 an aluminum pipe (3.5 cm. internal diameter, 4.2 cm. external diameter) having 92 specially modified socket couplings (5.0 cm. external diameter) sealed with a quick-polymerizing synthetic rubber was sunk 226 m. in a vertical water-filled bore hole in Blue Glacier, Washington. U.S.A. The geometry of threads and mating surfaces of pipe and coupling was designed to cause increasing external water pressure to tighten the seal. One joint at a depth of 66 m. immediately developed an extremely slow leak (probably because of faulty cleaning), but the other 91 joints apparently were sound, as the pipe was free of water to a depth of at least 157 m. when resurveyed after one year.

During a visit on 31 August 196 1 to this glaciel', which is situa ted a bout 35 miles (56 km. ) east-north-east of Srinagar, it was noticeable that a considerable recession of the snout had taken place since its position was as shown on the one-inch Survey map of 19 12, and also on the reduced half-inch sheets of 1922 and 1943, all of which a restill in current, but politically restricted, use. There has been retreat in the interval of about half a mile (0·8 km.), i.e. from the lower open valley to the vicinity of the north face of Mt. Kolahoi, where it descends in a nice fall fed chiefly by the upper glacier basin to the west.

Coefficients of absorption of visible radiation are determined for sea ice and snow as a function of porosity of the medium and wave-length of energy refracted into it. A comparison is made between the values derived and those obtained by other investigators under similar snow conditions. A difference in results suggests a significant rôle of crystal size and orientation in the absorption properties of sea ice and snow.

Gravity studies indicate that the Sukkertoppen ice cap is about 400 m. thick. The annual snow accumulation increases westwards from about 13 g. cm.−2 near the eastern edge of the ice cap to about 34 g. cm. −2 near Mount Atter, in the south-west. Probably all of the ice cap is “temperate”.

Discussions of possible causes of preferred crystal orientations in fresh-water ice are presented, with data on ice orientations from several Arctic lakes. Evidently, initial ice orientations are determined by wind conditions. Orientation selection during growth at the bottom of the ice also takes place, but in the lake ice examined it is apparently largely unsystematic. Constitutional supercooling can cause c-axis-horizontal orientations, but it is not of sufficient magnitude in the lakes examined to have much effect. Striations are locally significant but erratic.

A thermal ice drill using a silicon carbide electrical resistance element has been developed. The silicon carbide element is operated bare in water, permitting a very simple and efficient drill design. Maximum operating power density in these elements is limited to 400 W./cm.3 by the tendency of wet silicon carbide to deteriorate rapidly at high current levels. The elements are readily replaceable and have a drilling life of 40 to 70 m. of hole. Normal drilling rates in ice of 5 to 6 m./hr. can be consistently maintained with 220 W. power input to the drill.