Clare Island Survey — Marine Algae. 



15 7 



(= 14-44° C.) runs up the coast of Norway, across the north of Sweden to 

 northern Russia and Siberia. Clare Island is situated on the same latitude 

 as Heligoland and Kiel, but, as will be seen later, the flora is of a very much 

 more southern type. 



The atmospheric moisture is of importance in connexion with the littoral 

 vegetation. But the problem of desiccation during low water is a very 

 complicated one, the latitude, together with the amount of wind and sunshine, 

 having to be taken into consideration. The following figures (" Irish Coast 

 Pilot," ed. 6, 1911) give the mean humidity for the Blacksod Point 

 Observatory for the last thirty-five years. It will be noted that the highest 

 figures are those of the winter months, whereas in the Faeroes the reverse is 

 the case, for which the absence in Ireland of summer fogs is probably 

 responsible : — 



Jan. 



Febr. 



Mar. 



Apr. 



May. 



June. 



July. 



Aug. Sept. 



Oct. 



Nov. 



Dec. 



88 



87 



86 



86 



81 



81 



84 



83 



84 



81 



86 



85 





N 



OTE. — ' 



Jbserva 



tions m 



ade at £ 



a.m. 



100 = 



Saturation poin 







2. Temperature and Salinity of the Sea. — Important as are atmospheric 

 conditions, the temperature of the water is even more intimately connected 

 with the algal vegetation. The direct influence of the former is confined to the 

 intertidal region, and is thus intermittent ; but the effect of the latter is much 

 more general, being felt both by the littoral and sub-littoral flora. A complete 

 series of observations on sea-temperatures at different depths is not available 

 for Clare Island ; but the Meteorological Office has favoured me with details of 

 the mean monthly surface-temperatures for Blacksod Bay and Cleggan during 

 the year 1911 ; and Mr. G. P. Farran has kindly supplied me with two sets of 

 temperatures and salinities for various depths in Clew Bay and off Clare 

 Island. From these it is evident that the surface temperature does not differ 

 much from that of 10-20 fathoms, so that the monthly table given below 

 affords a good general guide. The Blacksod and Cleggan observatories are 

 about twenty miles north and south respectively of Clare Island. It will be 

 noted that many of the Blacksod figures are slightly higher than those of 

 Cleggan, for which local topography doubtless accounts : — 



Mean Surface Temperature, Blacksod and Cleggan, 1911. (C°). 





Jan. 



Febr. 



Mar. 



Apr. 



May. 



June. 



July. 



Aug. 



Sept. 



Oct. 



Nov. 



Dec. 



Blacksod, 

 Cleggan, 



72 



7*2 



6-7 

 6-7 



6-7 

 67 



8-3 

 83 



11-7 

 111 



13-3 % 

 12-2 



16-1 

 13-3 



16-1 

 15-0 



13-3 I 106 

 13-9 10-6 



7-2 

 7 '2 



6-7 

 5-6 



