MARINE BIOLOGICAL STATION AT PORT ERIN. 45 
our sea, of enormous amount and far-reaching importance, 
which have been recently discovered, and in fact, are now 
being investigated, and may, I[ think, be new to most of you. 
I fancy we are in the habit of thmking of the sea as constant 
in character and composition throughout the year. I am, of 
course, excluding such changes as are caused by tides and 
storms, and perhaps I ought to exclude also changes in tempera- 
ture, for everyone knows that our sea is colder in winter and 
spring than in summer and autumn (the lowest temperature 
is usually in March, and the highest nm August), but it will 
probably be new to you to learn that the sea differs in specific 
gravity and salinity from time to time, that it differs very 
remarkably in its microscopic contents at the different seasons, 
and, further, the sea changes notably in its chemical character- 
istic of alkalinity. 
Let me tell vou a little more about this alkalinity of the 
sea, as another example of periodic change. Several scientific 
men have during the last few years independently worked at 
these chemical variations in the sea, and one of these is 
Professor Benjamin Moore, who first of all discovered while 
working at the Port Erin Biological Station that the sea around 
the Isle of Man was a good deal more alkaline in spring (say April) 
than it is im summer (say July); and then, on examining 
monthly samples taken throughout the year, he was able to 
show that the alkalinity, which gets low in summer, increases 
somewhat in autumn, and then decreases rapidly during the 
winter, and then after several months of a minimum, begins to 
increase again in March, and rapidly rises to its maximum in 
April. That is the periodic change of alkalinity, and it will be 
seen to correspond roughly with certain very important changes 
in the living microscopic contents of the sea, and the connection 
between the two may be made out by inquiry into the nature 
and meaning of the changes in alkalinity. The alkalinity of 
the sea is due to the relative absence of carbon dioxide, So 
