ON THE SALINITY OF THE SEA-WATER. 235 



H. triquetrum Br. and Schimp. 



On Forest, very common (2) ! ; Loughton (2) ! ; Epping 

 Forest (n)! ; nr. Chelmsford (7); N. Essex (14) ; 

 Chalkney Wood, Earls Colne (8) ! ; Saffron Walden (g). 



[The Club is greatly indebted to Mr. Chittenden, not 

 only for collating the information concerning the Museum 

 Herbaria of Mosses, and identifying doubtful examples, but also 

 for actually mounting and arranging the specimens. Mr. 

 Chittenden's work in this way has been of the highest Museum 

 value and a great aid to the Curator. — Ed.] 



ON THE SALINITY OF THE SEA-WATER 

 ALONG THE COAST OF ESSEX. 



By H. C. SORBY, LL.D., F.R.S., F.L.S., F.G.S., &C 

 [Read October 2~th, 1906.] 



FOR a number of years (1884 to 1888, both inclusive) 

 I systematically studied the salinity of the water along 

 the coast and in the estuaries of Essex, and found that 

 one of the most important facts in connection with the 

 distribution of the marine animals was the difference between 

 the density of the high and low water. My results, however, 

 apply only to the summer months, from the early part of May 

 to the latter end of September ; and no doubt they differ widely 

 from the conditions in winter. The comparative salinity was 

 determined by a hygrometer, which was far the most convenient 

 method on board a yacht. 



What struck me much was that in some years at Burnham 

 on-Crouch the density of the low water was greater than at high 

 water ; and, in passing up the river to Battles Bridge, the 

 density became greater and greater. To my surprise I found 

 the well-marked Alga, Chorda, growing in some quantity not 

 much below Battles Bridge in 1885, when the density of the 

 water was very high, but I looked for it in vain in 1885, when 

 the density was much lower. I do not remember seeing it 

 elsewhere along the coast of Essex. This excess in density in 



