58 SOUTHERN CALIFQiRNIA GEOLOGY 



The foregoing telegram from the Coast and Geodetic 

 Survey of date October 27, 1927, was followed by re- 

 ceipt of the letter therein mentioned. 

 Department of Commerce 

 U. S. Coast and Geodetic Survey 

 Washington 



October 29, 1927. 

 Dr. Robert T. Hill, 

 Los Angeles, California. 

 Dear Sir: 



Enlarging upon the information sent you in my night 

 letter dated Oct. 27, I wish to say that since the first 

 comparison was made of the geographic positions of 

 triangulation stations in California, resulting from the 

 work done in the field thirty or more years ago and 

 that done in the last few years, a complete readjust- 

 ment of the triangulation net of the western half of 

 the country has been made. That net was controlled 

 by many Laplace azimuths and base lines, with the 

 result that the adjustment shows great strength in 

 the various sections of the net. 



I am enclosing a copy of our serial No. 350, which 

 gives a brief account of the net adjustment which, I 

 think, will interest you. Under separate cover there 

 will be sent you a copy of No. 134. The closing errors 

 of several loops, shown in figure 8 of the latter publica- 

 tion, indicate very clearly the accuracy of the triangula- 

 tion in the western part of the country. 



The old geographic positions in California resulted 

 from triangulation in which no Laplace azimuths had 

 been used. A Laplace azimuth, as you no doubt know, 

 results from observations on Polaris corrected for the 

 deflections of the vertical at the point where the obser- 



