abstracts: geodesy 669 



the irregularities of distribution by continuous lines, hence the plan 

 was adopted of drawing the lines to represent the g Mineral distribution 

 and of entering on the chart isolated abnormal values differing by more 

 than a degree from the normal value for the locality. A disturbed 

 area of some extent, indicated by observations at several places, is 

 represented by a small closed curve. For this reason the lines on this 

 chart appear less irregular than those on the one for 1910 which it 

 supersedes. D. L. H. 



GEODESY. — ■A'pTpUcation of the theory of least squares to the adjust- 

 ment of triangulation. Oscar S. Adams. U. S. Coast and Geodetic 

 Survey, Serial No. 9, Special Pubhcation No. 28. Pp. 220. 1915. 



This publication has not been prepared with the idea of displacing 

 the textbooks in dealing with the subject of least squares but of supple- 

 menting these in the special field of triangulation. Concrete examples 

 of adjustments are given, ranging in difficulty from some of the easiest 

 to those thac are more difficult. A development is given, expressed in 

 the symbolism employed in the office of the Survey at the present time, 

 for the condition equations necessary to effect the closure in geo- 

 graphic positions of a loop. A need for this has been felt for some time 

 past. A method of adjustment by the variation of the geographic 

 coordinates (latitude and longitude) of the various points has been 

 developed and applied to the adjustment of several figures. This is 

 a method which has not heretofore been used in the United States, 

 although something similar is regularly employed in Canada. 



At the end of the publication there is given a new development of 

 the formulas for the computation of differences of elevation from the 

 observations of zenith distances. These formulas take into account 

 some of the effects due to the lengths and heights of the lines that 

 were not taken into consideration in the development previously in 

 use in the Coast and Geodetic Survey. O. S. A. 



MINERALOGY. — A71 arrangement of minerals according to their occur- 

 rence. Edgar T. Wherry and Samuel G. Gordon. Proc. Acad. 

 Nat. Sci., Philadelphia, 1915: 426-457. Aug. 24, 1915. 

 The types of mineral occurrence are classified on the basis of chemical 

 and geological relations, the chief criterion for subdivision being dis- 

 similarity in mineral content. About 800 species of minerals are ar- 

 ranged according to this classification, and an alphabetical index for 

 locating the position of any species is given. E. T. W. 



