Many hitherto unexplained erratic gravimeter measurements can be attributed to the effect of vibration on the gravimeters during transportation between gravity stations. Experiments with four LaCoste and Romberg land gravimeters on a vibrating platform showed that all are affected to some degree by forced vibrations at frequencies and peak accelerations that can occur on common carriers. Two effects were found: all four gravimeters when subjected to vibration in the 35‐ to 70‐cps range for 1 min or more at peak accelerations of about ±1 g drifted erratically in the ±0.1‐mgal range; at about 48 cps positive drift as rapid as 1 mgal/min sometimes occurred. The threshold of acceleration needed to produce this unidirectional drift varied from ±0.5 to ±2.0 g for the meters that were tested. As there is extensive documentation to show that vibration of these intensities may occur at frequencies in this range in aircraft or land vehicles, it is concluded that vibration is the major cause of the inconsistent performance that is occasionally observed on these instruments. In experiments with foam rubber and mechanical isolators to minimize the effect of the ambient vibration field, it was found that by using mechanical isolators to support the gravimeter within the carrying case it was possible to eliminate the unidirectional drift at accelerations of ±2 g.

Gravity Map No. 88 covers the coastarea of British Columbia andincludes the continental shelf, Vancouver Island, the Queen Charlotte Islands and the fiords of the mainland. The Bouguer anomalies have been contoured at 10 mgal irl.tervals and are based on gravity measurements every 12 to 15 km. The terrain corrections have been computed using either a rectangular or a circular graticule or a combination of both depending on the scale of the available topographie maps. The major features of the gravity field are: a positive Bouguer anomaly along the western edge of the area, which is associated with the change from continental to oceanic crust, and a negative anomaly along the Coast Mountains which is attributed to the thickening of the continental crust below the se mountains. Over the eastern part of the Queen Charlotte Islands, Hecate Strait, Queen Charlotte Sound and Vancouver Island, changes in the Bouguer anomaly values have been related to density variations in the surface rocks.

The Dominion Observatory regional underwater gravity survey of the Gulf of St. Lawrence was continued in 1966 and 1967. Sorne 1,200 gravity stations have now been established in the Gulf during the period 1962-1967. Equipment and survey techniques used in the survey are described and the method of reduction of the underwater gravity results is reviewed. The Bouguer anomaly field over the norther portion of the Gulf of St. Lawrence is similar to that of the adjacent Precambrian Shield. A distinct change in anomaly level from negative in the north to more positive in the south occurs in the Gulf and is believed to mark the boundary between the Grenville and Appalachian geological provinces. Basic intrusive rocks characteristic of the boundary between these provinces are outlined by a belt of positive anomalies from Gaspé Peninsula to Port-au-Port Peninsula, Newfoundland. A gravity minimum of -60 mgal near Magdalen Islands has been attributed to abnormally light Carboniferous sediments or Devonian granitic rocks or alternatively their combined effect. The gravity anomalies between southwestern Newfoundland and Cape Breton Island suggest a structural continuity between these areas.