among the Shetland Isles. 303 



be seen in full force on the North American continent ten or 

 more degrees further south than in Europe." Possibly he 

 was misled by one of Forbes's conclusions (Rep. GeoL Surv. 

 p. 402), that " no glacial beds are known in Southern Europe." 

 This, however, was more than twenty years ago. I have 

 myself identified from the Calabrian and Sicilian deposits 

 several high-northern shells (e. g. Terehratula cranium^ T, sep- 

 tatttj Lima excavata^ Mytilus modiolus^ Gyprina Islandica^ Mya 

 truncata^ var. TJddevallensis^ Saxicava Norvegica^ Puncturella 

 Noachinaj Emarginula crassa^ Buccinum undatum^ and Natica 

 affinis or clausa)^ and from the Rhodian deposits Terehratula 

 septata and Lima Sarsii. 



My old companion, Mr. Waller, picked up on the beach in 

 a small bay on the west coast of Shetland a shell of Spirula 

 australis. It is a tropical Cephalopod, and is not unfrequently 

 thrown up by the waves on the southern and western shores of 

 England, Wales, and Ireland, together with exotic species of 

 Teredo J lanthina^ and Hyahea brought from southern latitudes. 

 Dr. Morch informs me that several shells of the Spirula have 

 this year been found in the Faroe Isles. The transport of 

 such tropical productions to northern latitudes has been usually 

 attributed to the Gulf-stream. It now, however, appears more 

 probable that this is the consequence, not of the direct action 

 and course of the Gulf-stream, but of the prevalence of 

 westerly and south-westerly winds, which waft onwards to 

 northern latitudes, in a northerly and north-easterly direc- 

 tion, the floating objects carried to a certain distance by the 

 Gulf-stream. The direct course of the Gulf-stream has not 

 been observed further north than about 45° N. lat. ; from that 

 point it would seem to dwindle into a north-easterly surface 

 drift. A chart will shortly be published by the Admiralty in 

 explanation of this view of the case ; and the following papers 

 on the subject ought to be consulted by physical geographers : 

 — Dr. Stark " On the Temperature of the Sea around the 

 coasts of Scotland during the years 1857 and 1858, and the 

 bearing of the facts on the theory that the mild climate of 

 Great Britain during winter is dependent on the Gulf Stream " 

 (Trans. E,. S. Edin. 1859), and Capt. Thomas's tables and re- 

 marks in Mr. Alex. Buchan's Report " On the Temperature 

 of the Sea on the Coast of Scotland " (Journ. Scottish Meteor. 

 Soc. Oct. 1865). See also ' Br. Conch.' vol. i. (Introd.) pp. 

 xcviii and xcix. 



I will add a short summary of the observations recorded in 

 my Reports on Shetland dredgings and in the work last cited. 



1. The bathymetrical zones have been too much divided by 

 Risso and subsequent authors. There are two principal zones, 



21* 



