NOTBS ON MAKIXE DEPOSITS OF THE FIRTH OF FORTH. 223 



harbour dredgers, which are constantly at this work. The deposit 

 beneath this again has more the character of an ordinary shallow- 

 water marine deposit. 



At Station II. the deposit was found to be similar in composi- 

 tion to that at Stations I. and III., with the exception that the 

 dead Turritella shells and other organisms are rare in comparison. 

 The deposit taken at Station IV. is more of a transitional 

 character than those found at Stations I. to III. Over the area 

 of Station IV. we pass through patches of a siliceous sand, which 

 again merges into grey sandy mud and shells or dark-blue mud, 

 similar to those obtained in and along the South Bay, till within 

 the 5-fathom line. Mixed with these deposits was obtained at 

 times masses of a blue plastic clay corresponding to material 

 taken from the new dock workings in course of construction at 

 Leith and deposited here by the harbour dredgers, all of which 

 tend in no small measure to obliterate the animal life at the 

 bottom. 



At Station V. a dark-brown or grey homogenous mud of fine 

 grain is found, which stretches over a considerable area inside 

 the 20fathom line to within a short distance of the May Island. 

 Many soundings were taken in this locality, all showing the 

 brown surface layer of river mud. 



At Station VI. a typical shell sand was found, and the Mollusca, 

 Foraminifera, and other animal remains which make up the bulk 

 of this deposit are of interest. The majority of these are seen to 

 be more or less infiltrated with a ferruginous-like substance, and are 

 for the most part of a deep ferric brown — some are brown, pinkish, 

 or white, and many of a greenish-grey colour j in some crystallization 

 has taken place, and the majority of the material which forms 

 this deposit, when treated with cold dilute hydrochloric acid, leaves 

 beautiful and perfect casts of the Foraminifera and many of the 

 other organisms, which, however, are very friable. This appears 

 to be due to some chemical combination, which has most probably 

 taken place inside the organisms themselves, and which I have 

 not yet been able to determine, a feature not uncommon in many 

 marine deposits, more especially in tropical and sub-tropical 

 regions, where in some localities it plays an important part in 

 forming phosphatic and other conglomerations on the sea floor ; it 

 is therefore of considerable interest to have found a similar 



