— XXVII — RAPPORT 1905—06 ANNEXE A 
taken into consideration for the time before August 1902, because standard water 
had not come into general use before this time and the determination therefore 
can not be directly compared with later determinations. Only such salinities have 
been included as have been found by standard water titration, accordingly none 
that are based upon areometer determinations. 
Surface Maps (Plates I and II) 
The surface maps have been constructed in the following way. The waters 
under observation are divided into fields each bounded by two longitudinal and 
two latitudinal circles but of different size, small ones in areas where the salinity 
changes much from place to place, larger ones where the variation of salinity is 
less or where there are very few observations. 
North of 54° N. Lat. and west of 7° E. Long. the sides of the fields are 
1 degree of longitude and 2/s degree of latitude; north of 57° N. Lat. and east of 
7° E. Long the sides are 1/2 degree of longitude and ‘/4 degree of latitude; south 
of 57° N. Lat. and east of 7° E.Long., the divisions are t}2 degree longitude by 
2/3 degree latitude, and south of 54° N. Lat. they are bounded by 2/3 degree longi- 
tude and ‘2 degree latitude. For all the observations that are included in one 
field the mean salinity is calculated and besides the mean position of the places 
of observation is determined. The way in which this has been done is that all 
the places of observation, except when they belong to the permanent stations, are 
put down as points on the same map whereupon is determined at a rough estimate 
the center of gravity for them and any station point that happens to be included 
in the field, the weight used for the station point being proportional to the number 
of observations at the station. 
Thus it has been possible on a map to mark out a mean position for each 
of the said fields and therewith to connect a mean salinity and a statement of the 
number of observations within the field in question. The mean positions as a rule 
range themselves in series extending north—south and east—west. For each of 
the corresponding series of salinities those points of the chosen isohalines that fall 
within the series are determined in the following manner by graphical adjustment. 
The mean positions in an east—west series, if they have very different latitudes, 
are projected on a circle of latitude, that approximately represents the mean lati- 
tude of the series, and the corresponding salinities, after having been somewhat 
corrected if necessary, by means of the nearest mean values, are referred to the 
projections. The circle of latitude is then stretched out in a straight line and its 
points of intersection with the isohalines are determined by graphical adjustment. 
The north—south series are treated exactly in the same manner (projection on a 
Iv* 
