26 HAYFORD 



sented by Japan, and this continent by the United States and Mexico. 

 In South America, Brazil, the Argentine Confederation, Chili and 

 Peru, are organizing geodetic surveys and will doubtless become 

 parties to the convention which recognizes the determination of the 

 earth's figure and size as an international function. As the arc of 

 Peru, which was recently remeasured by the French, was measured 

 by a European nation, the United States is the only country among all 

 the American nations, which has contributed to our knowledge of 

 the earth's figure. Leaving out of consideration for the present several 

 minor arcs along the Atlantic seaboard the Coast and Geodetic Survey 

 published in the year 1900 the results of the measurement of the trans- 

 continental arc along the 39th parallel. This was followed in the 

 year 1901 by an account of the oblique arc extending from Eastport, 

 Maine, to New Orleans, La. Since then it has published the results 

 of its trigonometric survey extending from the southern boundary of 

 California to Monterey Bay, California. These great triangula- 

 tions were begun in many separate localities and when they were 

 connected it became necessary to adopt a uniform system of coordi- 

 nates for the whole country. The advantage of doing this was recog- 

 nized by the engineers of the Army, under whom an extended trigono- 

 metric survey covering the region of the Great Lakes had been 

 completed, and their triangulation, 1 aving been connected with that 

 of the Coast and Geodetic Survey, was, by cooperation between the 

 Departments having charge of these organizations, referred to the 

 same datum adopted by the Coast and Geodetic Survey. The earlier 

 coastwise triangulations of the Coast and Geodetic Survey were pro- 

 jected upon the Bessel spheroid. As the work progressed it became 

 evident that the Clark spheroid of 1S66 was in the region of the United 

 States better adapted for the purpose of a reference spheroid than the 

 former, and it was substituted for the Bessel spheroid. It also became 

 clear that for purely geographic purposes the Clark spheroid would 

 suffice, or at any rate that an attempt to substitute, if it were possible, 

 a closer osculating spheroid would involve enormous labor without 

 compensating advantages. This point of view established the policy 

 of referring all the trigonometric work on the United States to a com- 

 mon origin of coordinates on the Clark spheroid of 1S66 on which 

 much of it had already been developed. 



Side by side with the computations necessary in this great under- 

 taking the investigation of the form of the geoid involving the anom- 

 alies which were developed by the trigonometric and astronomical 

 operations was carried on, for the adoption of a reference spheroid 



