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SCIENCE. 



[N. S. Vol. XXIV. No. 623. 



barometer and simultaneously the pressure 

 is also determined in absolute units by an 

 accurate observation of the boiling point 

 of water, using mercurial thermometers. 

 From these simultaneous observations the 

 intensity of gravity at the point of ob- 

 servation is computed. This method is 

 entirely successful in determining gravity 

 with the accuracy necessary for an effective 

 study of the anomalies in gravity. This is 

 the only successful method yet devised for 

 determining gravity at sea with sufficient 

 accuracy. Such observations are of ex- 

 treme importance to geodesy, because they 

 are the only geodetic measurements possible 

 over three fourths of the globe. Hecker's 

 observations show that, in general, over the 

 deep Pacific gravity has nearly its nor- 

 mal value, as computed by Helmert's for- 

 mula of 1901, fixing the relation between 

 gravity and latitude. Parenthetically, it 

 may be remarked that this indicates that 

 the condition called isostasy exists. Four 

 regions with large anomalies, with refer- 

 ence to Helmert's formula, were found. 

 Near Oahu, one of the Sandwich Islands, 

 gravity is considerably in excess at sea, 

 just as it has already been observed to be 

 on the island. There is a region of excess- 

 ive gravity in shallow water near New 

 Zealand. Over the submerged Tonga pla- 

 teau, where the depth is 3,000 meters, grav- 

 ity is largely in excess and in the adjacent 

 Tonga deep (5,000-10,000 meters) there is 

 a large defect of gravity. 



H. Kimura, of Japan, reported on a 

 harmonic analysis of the variation of lati- 

 tude which has been made by him. The 

 analysis develops the very interesting fact 

 that in addition to its other motions, al- 

 ready approximately known, the pole has 

 a reciprocating motion approximately 

 along a straight line, with a period of about 

 0.75 year, a period which is not commen- 

 surable with any of the other known 

 periods of the polar motion. 



Lallemand, of France, for many years 

 the authority on precise leveling, stated 

 that a series of experimental comparisons 

 had been made in France between the 

 French instrument and method and the 

 instrument and method used in the U. S. 

 Coast and Geodetic Survey since 1900. The 

 conclusion reached was that the degree of 

 accuracy is sensibly the same in the two 

 cases, because in each the instrumental 

 errors have been made so small that the 

 errors in the results are mainly due to 

 meteorological conditions, that is to con- 

 ditions between the object glass and the 

 rod. 



On the part of our own country there 

 was presented a special report upon a re- 

 cent determination of the figure of the 

 earth, made by the Coast and Geodetic 

 Survey and based entirely upon deflections 

 of the vertical observed in the United 

 States. This report showed that to secure 

 the highest degree of accuracy in such de- 

 terminations the theory of isostasy must 

 be taken into account; that the United 

 States is not maintained in its position 

 above sea level by the rigidity of the earth 

 but is, in the main, buoyed up, floated, 

 because it is composed of material of defi- 

 cient density; and that the defect of 

 density is limited to the depth of 71 miles, 

 if it is uniformly distributed with respect 

 to depth. This report, if it is convincing, 

 must ultimately produce radical changes 

 in the methods of computation used by 

 geodesists. It also has a direct bearing 

 upon several of the greater problems of 

 geology and of geo-physics. 



The activity of the association itself, as 

 distinguished from the activities represent- 

 ed by reports of progress and special 

 papers, is indicated by the fact that the 

 average rate of expenditure for the past 

 three years has been $19,000 per annum. 

 This covers administration, printing and 

 postage, the maintenance of the central 



