TJ. @. COAST AND GEODETIC SURVEY — ROBERTS 229 



prepared. In 1850, processes had been so speeded that the first sheets 

 from the west coast resulted as published charts within 20 days. The 

 Bureau gradually assembled a large group of skillful men whose 

 artistry resulted in some of the most beautiful chart engravings ever 

 seen. This craft endured until recent years, to be supplanted at last 

 by newer methods of glass-negative engraving and photolithography, 

 developed largely in the Survey in the unromantic cause of efficiency. 



The first years of chart production saw perhaps 4,000 copies pro- 

 duced in a year. These were all nautical charts. With the advent 

 of aviation and the sudden great growth of air navigation, the 

 bureau had thrust upon it a duty of supplying aeronautical charts 

 as well, a duty which multiplied the cartographic and printing work 

 many times. A vast number of general aeronautical charts have been 

 required — World Aeronautical Charts, regional, sectional, and route 

 charts — as well as special facility and airport approach and landing 

 charts. The multicolor presses of today have delivered more than 43 

 million nautical and aeronautical charts in a year, many of them 

 printed cooperatively to augment the reproduction facilities of the 

 Hydrographic Office and other Federal chart agencies. The de- 

 velopment of the crude chart of olden times into a highly specialized 

 instrument of navigation has involved a long series of changes, sim- 

 plification, and adaptation. Chart use is now complicated by the 

 requirements of high-speed navigation, radio, and radar techniques, 

 and other new practices not dreamed of in the early nineteenth 

 century. 



Sea-level studies, the handmaiden to hydrographic surveys, have 

 had to be carried on. Tide gages were widely distributed and the 

 analysis of tidal regimes begun in 1853, permitting the publication 

 of tide predictions for use in ship operations. Assistant Joseph 

 Saxton invented an automatic-recording tide gage. Basic hydro- 

 dynamic theories of tidal motion were later developed by Assistant 

 William Ferrell and elaborated by mathematician Rollin Harris. 

 They brought weird notions of the ocean pulse into systematic order. 

 Harris and Fischer built a tide-predicting machine capable of in- 

 tegrating the phases of 37 separate harmonic components into the 

 complex tidal curve. These activities earned the Survey the primary 

 responsibility in the United States for tidal investigations, and the 

 publication of worldwide tide and tidal-current predictions is now 

 effected by the Survey, in cooperation with the Navy, which has the 

 basic responsibility for the foreign-area work in this field. 



The laborious chaining method of surveying shore areas and land- 

 marks necessary in coasting and piloting has gradually given way 

 to the planetable and stadia rod, to photography, and finally to air 

 photogrammetry, which quickly and accurately provides the infor- 

 mation needed for the compilation of detailed topographic maps. 



