SUNIER: Marine fish-ponds of Batavia. 179 
The figures relative to the ponds op Kampong Jaagpad set forth in 
Table VI show that on the first four days of February 1919 the salinity in these 
ponds, taking the; average of 8 cases, amounted to 35.9 °/,,. On the 4th even 
a salinity of 40.1°/, was observed. On the 5th however, the salinities 
observed only amounted to 22.7°/,, and 13.2°/o9, whilst on the Oth day of 
the month already a salinity as low as 3.4°/,, was observed. The explanation 
of this phenomenon is found in the fact that the first heavy West-monsoon rains 
in 1919 (according to data supplied by the Royal Magnetical and Meteorological 
Observatory, Weltevreden) did not come down till the nights of the 4th 
to 5th, and the 5th to Oth days of February. At8 o’clock in the morning of 
February 5th the rain-gauge at Tandjong Priok was tapped of 32 mm. of rain, 
on the morning of the 6th, also at 8 o’clock, this rain-gauge showed 94 mm. 
Whereas therefore the increase of the salinity in the course of the 
East-monsoon from the nature of the case is a very gradual one, very 
sudden decreases of the salinity may occur in afew hours during the West- 
monsoon. No facts have come to my notice tending to show that these 
fairly sudden and considerable decreases of the salinity should have a 
lethal effect on the animals living in the empangs. As to the influence 
of high salinities on the animals and plants living in the empangs, the 
reader is referred to Chapters IV to VIII. 
In conclusion I must for a moment revert to the statement already made in 
passing, that the salinity of different samples of water drawn at the same time and 
from the same pond but atdifferent places situated afew hundred metres apart, may 
reveal differences of several units pro mille, as appears from the following table : 
Salinity wat Distance between the two Sain Fe Difference be- 
Beene D point ao. two | Pern ee 
GRIND Rel One less: thanks KIM. 73) Oleg 6.8 "on 
io ONEENS Gem | ENE Ee 24.7 Ooo | 80 ‘Jo 
1a WS. NE PO DI Olio 6.65 Jo 
15 Wil AE 20.0 hp | fy ” Sn Fi 24.6 0/00 | 3.0 0/60 
SD MITA MECS OMIS NRA Pr 3520 5.9 oo 
I VO re UN ea à 18.3 °/00 3.2 0/00 
DOON Nee Ole 09 a RORE 13820, A On 
A SIO LOO BANE AE 46.5 fog 2.7 en 
This phenomenon will most likely be connected in the first place with 
the different distances of the two points of observation from the places where 
salt, brackish or fresh water can be admitted and where pond-water can 
be discharged. Further local differences of insolation or of shelter 
from the wind may produce differences of salinity. It should be remembered 
in this connection that diffusion takes place so slowly that it does not 
make its influence felt very quickly. 
