MARINE BIOLOGICAL STATION AT PORT ERIN. 67 



turnover of colossal extent amounting' to between 20,000 

 and 30,000 tons of carbon per cubic mile of sea-water. 

 Or, if we think of the carbon as being present in tbe 

 bodies of living organisms, then tbe weight of these 

 organisms will amount to about ten times the above 

 amount, viz., about 300,000 tons per cubic mile — or, if 

 we imagine these organisms distributed along the 

 deepest part of the Irish Channel, then they would 

 occupy a strip of water about 10 miles long by one mile 

 wide and 88 fathoms deep — all of which organisms have 

 obtained their carbon from the carbon-dioxide present 

 in the water in spring. 



Professor Moore is continuing his observations upon 

 the condition and changes of the sea-water monthly 

 throughout the year. 



.The alkaline reaction of the sea to phenol-phthalein 

 indicates, moreover, the absence of free carbon-dioxide. 

 It thus follows that, during the summer, plants in the 

 sea must obtain their carbon from the decomposition of 

 carbonates or bicarbonates in the water — probably from 

 these salts of magnesium — and not from carbon-dioxide 

 as they presumably do in spring when the water gives 

 an acid reaction. 



Thus we are led from the observation of the minute 

 organisms on the beach to some of the greatest problems 

 in connection with the chemical and biological changes 

 going on in the ocean ; but it need not be thought by the 

 young naturalist that he must necessarily adventure 

 forth on to the high seas in pursuing his quest. Some 

 investigators must, no doubt, do so; but there remains 

 plenty of useful work to be done on the beach and in the 

 laboratory in carefully examining with the microscope 

 the various deposits, such as sand and mud, found 

 between tide-marks, not once for all, but periodically, so 



