208 Mr. Waldie’s investigations connected [No. 3, 
Influence of the Tides. 
It will indeed be convenient to take up this subject first in order. 
Dr. Macnamara’s results exhibit-very clearly the increased quantity of 
saline constituents during the hot season, commencing in March, and 
coming to its height just before the commencement of the rains. His 
table shews as much as 77.7 gyrs. dry saline residue from 1 gallon of 
water at high water on 12th June, 1862. Lobtained from water taken at 
full spring tide, on 14th June of this year 1866, as much as 106.3 ers. 
per Imp. gallon. This is easily accounted for when it is found, as ascertain- 
ed from examination of the rainfall, that from June 1861 to end of May 
1862 there had fallen 87.4 inches of rain, while during the correspond- 
ing period of 1865-66 there had been only 47.9 inches: the river 
must have been much lower and its current feebler, and consequently 
the sea water had penetrated farther. My observations were all made on 
water taken from the river near my own residence at the viliage of 
Baranagur or Barnagore, with a few exceptions which I shall notice 
afterwards. The locality is about two miles above Cossipore. But I 
made observations also on the effect of time of tide. 
This point is also noticed in Dr. Macnamara’s report, though not 
very fully. He mentions that the water varies much in the degree of 
its impurity with the time of tide, falling as low during April and May 
as 23° at low water, that is, 23 grains of saline matter in 1 gallon. My 
observations indicate even a greater amount of variation than is by this 
suggested, as will be shown by the table I have prepared. As the 
evaporation to dryness and weighing the residue of numerous samples is 
very tedious and troublesome, another plan was adopted for estimating 
the amount of variation. The river water proper contains very little 
chlorine in its composition, while in the state of common salt this is 
the characteristic constituent of sea water. The quantity of chlorine 
was therefore ascertained by the usual volumetric process with nitrate 
of silver, and calculated as if it existed entirely as chloride of sodium 
or common salt, which afforded a very good means of comparing the 
samples and estimating the proportion of sea water present. 
I endeavoured to make some observations further up the river, but 
found that it could not be done properly except with an expenditure 
of time, trouble, &c. that I could not devote to it. Any observations 
that I did make were only confirmatory of Dr. Macnamara’s results. 
The following table exhibits the results of my observations on the 
