172 TREUBIA VOL. Il, 2-4. 
Now, repeating this calculation and applying the approximate salinity 
of 88.5°/,), we arrive at the following: 
1 Volume of fish-pond water of 28° C. and of a salinity of 88.5°/,, = 
1.00404 weight-units of fish-pond water. Therefore in 2.98878 + 1.00464 = 
4.05342 weight-units of the mixture of three volumes of distilled water 
and one volume of fish-pond water there were present == X 4.05342 = 
0.094445 weight-units in salts. These salts had been contained in the 1.06404 
weight-units of pond-water. Each weight-unit of this pond-water therefore 
contained 0.0887 weight-units in salts, or, in other words, the salinity of 
the pond-water was 88.70/,, instead of 93.2 °/o. 
The dilution of 1 volume of pond-water with 3 volumes of distilled 
water occurred but a very few times. 
In diluting one volume of fish-pond water with one volume of distilled 
water the error is smaller. We take the example of a high salinity, viz. 
73.4 °/o,, found by an areometer-reading on diluting one volume of fish-pond 
water with one volume of distilled water. The same calculation as the 
above shows that the real salinity was only 71.5 %/oo- 
The dilution of one volume of pond water with one volume of distill- 
ed water therefore yielded a salinity which, apart from the errors inherent 
in the areometer-method and its application, was too high by about 1.9 °/,, 
or less; the dilution of one volume of fish-pond water with three volumes 
of distilled water yielded a salinity which was too high by about 
OM OF less. 
On determining the salinity of a sample of fish-pond water, first 
by mixing equal volumes at a temperature of 27.6° C.; and afterwards by 
mixing equal weights of fish-pond water and distilled water, I found suc- 
cessively 63.9 °/ ) and 62.9 foo. 
§ 2. Discussion of the data collected and elaborated. 
From March 5th 1918 onward I determined with fair regularity the 
salinity of the fish-pond water in a number of places in Mr. Görs’s system 
of ponds. These points are marked on Map Il with the digits 1—7, 3a and 
7a in the ponds A to G and C’ inclusive. All the salinities observed in 
these places have been collected in Table I. 
The letters L, M, z and Z occurring in this Table I under the number of 
the points of observation, have the following meanings: 
L (Land) signifies that the point of observation is situated near the 
land-boundary of the pond-system; Z (Zee — Sea) signifies that the point 
of observation is in one of the outer ponds, nearest the sea; M means 
that the observation point is situated about the middle, or balfway between 
the land and the sea- boundaries of the pond-system. z Denotes that 
