Gravity Measurements in North America with the Cambridge Pendulum Apparatus. II
Proceedings of the Royal Society A
The m ethods described in the first paper of this series have been used to establish ten further pendulum stations, extending from Lethbridge, Alberta, to Fairbanks, Alaska. A range of over 4300 mgals is thus covered by the observations made in N orth America with the Cambridge pendulums. As was done previously, the value 980'6220 cm /s8 has been tentatively adopted for O ttawa. On this basis, the value obtained for Fairbanks, the m ost northerly station, is g Fairbanks = 982-2477 cm /s8. I n t
... r o d u c t i o n In the first paper of this series (Garland 1953, referred to hereafter as I) the desirability was mentioned of establishing in North America a calibration range for gravimeters, by means of pendulum observations at points extending over a wide range of gravity. The results of the first series of measurements, extending from Mexico City to Winnipeg (latitude 50°) were given in I. During the summer of 1953, the calibration line was extended by similar measurements to Fairbanks, Alaska (latitude 65°). The total range of gravity covered by the observations is thus increased to over 4300 mgal. The two series of stations are not actually located on a continuous north-south line (figure 1), as it was necessary to choose the northern sites along the Alaska Highway between Edmonton and Fairbanks. Nevertheless, by taking advantage of air transportation, it would be possible to observe with a gravimeter at such points as Houston, Edmonton and Fairbanks within a few hours. In order to make the observations of the two seasons as consistent as possible, a connexion between Ottawa, Winnipeg (a station of 1952) and Edmonton (the base for 1953 observa tions) was made in the spring of 1953. D e s c r i p t i o n s o f s t a t i o n s The geographical co-ordinates, elevations and locations of the stations relative to their surroundings will be summarized in this section. For convenience to those reoccupying the points, sketches of the locations are given in figure 2 . The stations are listed in the order in which they were observed. ( 1) Edmonton, Alta. Basement of the Arts Building of the University of Albert a, in the south-west corner of the Physics Laboratory. The site is identical with that of Miller (1929). Latitude 53° 31-3', longitude 113° 31-3', elevation 2197 ft.