36 



SCIENCE. 



[N. S. Vol. XVIII. No. 445. 



century it was held an open question by 

 some whether the work should be coordi- 

 nated by purely astronomical observations 

 or whether it should be based on a trig- 

 onometric survey, and happily the latter 

 method was chosen and prescribed. 



From carefully measured bases chains of 

 triangles were to be extended along the 

 coasts. Their direction and geographical 

 location were to be determined by astronom- 

 ical observations. The skeleton of tri- 

 angles was to be clothed by the topographer, 

 who should delineate the topographic fea- 

 tures as far as might be necessary for com- 

 merce and defense. By making proper use 

 of the trigonometric and topographic fea- 

 tures thus determined the hydrographer 

 would follow and sound the depths of the 

 waters, develop the channels fit for safe 

 navigation, discover all hidden dangers, 

 measure the tides and the currents, and 

 thus furnish what was needful for a safe 

 chart. As a matter of fact, this sequence 

 of work, though it is of necessity observed 

 in local surveys, was never followed when 

 the Coast Survey as a whole is consid- 

 ered. The rapid commercial development 

 of this country made it necessary to meet 

 particular demands in some localities at 

 once, leaving others of lesser urgency to 

 be dealt with later on, but the general 

 scheme of proper coordination by a prin- 

 cipal triangulation was never lost sight of, 

 though the latter oftentimes followed long 

 after the local surveys had been made. 

 This experience is being repeated in Alaska 

 and particularly in the Philippine Islands, 

 where the survey is constrained by the 

 needs of commerce to make surveys here 

 and there, v?herever routes of travel or 

 anchorages have to be developed, leaving 

 it to the futvire progress of the survey to 

 coordinate all this work. 



The distances of the stars, the sun and 

 the moon from the earth as we know them 



have all been measured, to use the language 

 of a former astronomer royal of England, 

 by means of a yard-stick. For the purpose 

 of this illustration it is immaterial that 

 the particular yard-stick of this survey is 

 the meter. The point is that with a short 

 bar we measure a relatively long base, from 

 this we extend a triangulation over rela- 

 tively much longer distances, from these 

 distances we deduce the size of the earth 

 and its diameters and thus have found the 

 basis of all dimensional astronomy. The 

 triangulation of the Coast and Geodetic 

 Survey, therefore, subserved not only its 

 immediate purpose of serving as a basis for 

 accurate charting of the coasts, but con- 

 tributed by its great extension to a knowl- 

 edge of the earth's dimensions and figure, 

 a problem which has occupied the mind 

 of man since Eratosthenes, 300 B.C., to 

 the present time. For the survey has com- 

 pleted a triangulation from Eastport, 

 Maine, to New Orleans, Louisiana, a dis- 

 tance of 2,400 kilometers, and another from 

 Cape May to San Francisco along the 39th 

 parallel, a distance of over 4,000 kilometers. 

 It is just now engaged in extending another 

 great chain of triangles, which has beert 

 measured between the southern boundary 

 of California and a point beyond San 

 Francisco, towards Puget Sound, where in 

 turn it will be connected with our northern, 

 boundary. Along the 98th meridian also 

 a chain of triangles is being measured, and 

 it is hoped that the Republic of Mexico 

 on the south and Canada on the north will 

 prolong its measurement through their re- 

 spective domains. Branching from this 

 meridian a line will cross to the eastward 

 to connect with the admirable triangulation 

 of the Lake Stirvey which has already 

 been connected with the primary triangula- 

 tion of the Coast and Geodetic Survey in 

 other places. 



The great triangulation already com- 



