46 University of California Publications in Zoology [Vol.15 



and longitudes are repeatedly tabulated without regard to the possible 

 error involved. 



(c) Meaning and nse of sections. — In making certain biological 

 and hydrographie investigations it is necessary to compare small areas 

 of approximately the same size which differ from each other in their 

 distance from the coast, average depth of water, nature of bottom, 

 and so on. As an aid to such investigations the region explored, or 

 likely to be explored, by us has been divided into rectangular areas, 

 or .sections, each containing approximately twenty-five square miles. 

 To be more precise, the sections were, for convenience, so chosen that 

 the length of their north and south boundaries would be five minutes 

 in longitude, while that of their east and we.st boundaries would be 

 five minutes in latitude. In defining them two base lines were chosen 

 and each section was designated by a nuniber giving its position west 

 of one base line, and either a subscript giving its position north, or an 

 exponent giving its position south of the other base line. 



To avoid complications arising from sections lying ea.stward as well 

 as westward from the north and south base line, the meridian of 114° 

 W was chosen and, since the region thus far explored lies, in the main, 

 between the parallels of 32' and 34° N, the former was chosen as the 

 second base line, thereby reducing the u.se of exponents and large sub- 

 scripts to a mininuim. Thus, as illustrated in figure 4, 24j, defines 

 the twenty-fourth section west of 114° W and the eleventh section 

 north of 32° N, while 24" defines one whose distance we.st of 114° W 

 is the same but which is the eleventh one south of 32° N. 



It is evident that, since each section measures five minutes on a 

 side and includes all positions \\'ithin 2f5 of its centre, the latitude and 

 longitude of any observation bears a definite and simple relation to 

 the number and subscript (or exponent) of the section as indicated 

 by the following formulae : 



A" = 12 (long?— 114°) 

 S = 12(lat? — 32°) 

 .B = 12(32? — lat?) 



where N is the section number, S the section subscript, E the section 

 exponent, and where the latitude and longitude are expressed in de- 

 grees to the nearest 5', or twelfth of a degree. Thus the section cor- 

 responding to 33° 12fl N and 118° 6:3 W is such that its center will lie 

 at the intersection of 33° 10' N and 118° 5' W, whence 



