434 



Mr Eattray on the Distribution of 



grown CD objects that have been submerged in sea water in 

 a clean condition, and after exposure for definite periods 

 been re-examined, with a view to the determination of 

 the habit and rapidity of growth, &c. * of the species iu 

 question : — 



By chauging the external conditions, considerable varia- 

 tions have been produced with respect to the foregoing 

 results. These changes have been effected by modifying 



* In connection with the consideration of rapidity of growth, which, when 

 taken in a relative light, so greatly influences the general fades of the Flora, 

 the observations by Mr Keill on the Carr Eock, at the entrance to the Firth — 

 a rock which is just uncovered at the lowest ebb of spring tides — are not 

 without interest. He says: — "A stone beacon was being erected on a low 

 rock called the Carr, near the entrance of the Firth of Forth. ... It was at 

 this time completely covered with the larger Algse, especially Fucus esculentus 

 and F. digiUiAus. By the necessary preparations for the beacon these were 

 cleared off, and the rock reduced to a bare state by the beginning of November 

 1813, when it was obliged to be abandoned for the winter. The coating of 

 sea-weed had at first been cut away by the workmen, the roots or bases after- 

 wards trampled by their feet, and much of the surface of the rock had been 



