26 president's address. 



July). The alkalinity, which gets low in summer, increases somewhat 

 in autumn, and then decreases rapidly, to disappear dmng the winter; 

 and then once more, after several months of a minimum, begins to 

 come into evidence again in March, and rapidly rises to its maximum 

 in April or May. This periodic change in alkalinity will be seen to 

 correspond roughly with the changes in the living microscopic contents 

 of the sea represented by the phyto-plankton annual curve, and the 

 connection between the two will be seen when we realise that the 

 alkalinity of the sea is due to the relative absence of carbon dioxide. 

 In early spring, then, the developing myriads of diatoms in their 

 metabolic processes gradually use up the store of carbon dioxide accumu- 

 lated during the winter, or derived from the bi-carbonates of calcium 

 and magnesium, and so increase the alkalinity of the water, till the 

 maximum of alkalinity, due to the fixation of the carbon and the reduc- 

 tion in amount of carbon dioxide, corresponds with the crest of the 

 phyto-plankton curve in, say, April. Moore has calculated that the 

 annual turnover in the form of carbon which is used up or converted 

 from the inorganic into an organic form probably amounts to some- 

 thing of the order of 20,000 or 30,000 tons of carbon per cubic mile 

 of sea-water, or, say, over an area of the Irish Sea measuring 16 square 

 miles and a depth of 50 fathoms ; and this probably means a production 

 each season of about two tons of dry organic matter, corresponding to 

 at least ten tons of moist vegetation, per acre — which suggests that 

 we may still be very far from getting from our seas anything like the 

 amount of possible food-matters that are produced annually. 



Testing the alkalinity of the sea-water may therefore be said to be 

 merely ascertaining and measuring the results of the photosynthetic 

 activity of the great phyto-plankton rise in spring due to the daily 

 increase of sunlight. 



The marine biologists of the Carnegie Institute, Washington, have 

 made a recent contribution to the subject in certain observations on 

 the alkalinity of the sea (as determined by hydrogen-ion concentration), 

 during which they found in tropical mid-Pacific a sudden change to 

 acidity in a current running eastwards. Now in the Atlantic the Gulf 

 Stream, and tropical Atlantic waters generally, are much more alkaline 

 than the colder coastal water running south from the Gulf of St. 

 Lawrence. That is, the colder Arctic water has more carbon dioxide. 

 This suggests that the Pacific easterly set may be due to deeper water, 

 containing more carbon dioxide ( = acidity), coming to the surface at 

 that point. The alkalinity of the sea-water can be determined rapidly 

 by mixing the sample with a few drops of an indicator and observing 

 the change of colour; and this method of detecting ocean currents by 

 observing the hydrogen-ion concentration of the water might be useful 

 to navigators as showing the time of entrance to a known current. 



