THE HARP SWELL LABORATORY 509 



reader, it will lie necessaiy to describe briefly the geography of the 



region. 



No geologist has described the rock formation of Casco Bay, al- 

 though many of the more salient points in its history are evident. A 

 glance at the accompanying map will show that the bay is dotted here 

 and there with islands, none of which are more than three miles in 

 length. It is popularly said by the denizens of the region that there 

 are as many islands in the bay as there are days in the year. However 

 that may be, it seems to the traveler who is making his first visit by 

 the little steamer threading tlirough the devious passages between the 

 islands, tbat the estimate has been too meager. Extending down from 

 the mainland are several long ragged points of land. Harpswell is one, 

 Cape Small Point is another. The axes of these peninsulas lie parallel 

 with those of the islands and between the islands and the peninsulas 

 are deep lagoons bordered by the steep high sides of the islands. The 

 average depth of these lagoons is fourteen fathoms, although a greater 

 depth is reached in some places. At the westward. Cape Elizabeth 

 forms the boundary for the bay. 



A portion of the Arctic current flowing do^vn the Gulf of Maine from 

 the Greenland and Labrador shores is deflected into the immediate 

 vicinity of Casco Ba}', giving the cool water and the cool air charac- 

 teristic of the locality. The Gulf Stream lies beyond this cold current 

 and, while rarely a bit of the fauna of this stream comes into the bay, 

 its effect is practically nothing on the plant and animal life. The 

 dense fogs so characteristic of some of our other laboratories, nearer 

 the Gulf Stream, are nearly absent here. It is mainly for this reason 

 that one may safely use apparatus at the laboratory without in- 

 jury from rust and hydroxide and oxide depositions. The writer, dur- 

 ing the past season, used apparatus of great delicacy, such as is seldom 

 brought out of the city workrooms, in investigating the contractions 

 of muscle in various invertebrates, without any deleterious effect being 

 produced by its sojourn at the coast. 



The geological structure of the region is such that the retreating 

 tides leave tide-pools filled with a wealth of animals and plants. The 

 range of the tides is great, averaging fourteen feet. The cleavage 

 planes of the mica schist and slate are normal to each other so that 

 square or rectagonal holes are left for the formation of the tide-pools. 

 Here may be found Asterias, Strong ylocentrotus, Metridium, Tetra- 

 stemma, Carcinus, Cancer and dozens of other species. The algalogist is 

 well rewarded for any labor he may expend in working these pools. 

 The lagoons were gouged out in preglacial times and therefore the rocks 

 are bare and free from till and boulders to a great extent. The sub- 

 sidence of the whole region in later times has deepened the water 

 throughout the bay, and these deep lagoons are carpeted with immense 



