574 Correspondence — J. B. Scrivenor. 



postulated from its occurreace there, has accordingly been a wrong 

 inference. Brogger has argued that it migrated from America. It 

 -was abundant in the Crag seas, and occurs in derivative fragments in 

 the Drift beds, but it does not occur in the estuarine deposits or raised 

 beaches, proving that after the period of the Crag it became extinct 

 in Europe and has since been reintroduced. He regarded the cause 

 of its extinction as a mystery, since the group of estuarine shells 

 with which it is found has lived continuously in Europe since later 

 Crag times. 



In the course of his paper the author gave some interesting 

 information on the changes known to have taken place in the Baltic, 

 which at one time was a freshwater lake ; afterwards it became freely 

 open to the IS^orth Sea, and possessed an abundance of marine shells, 

 with Ostrea and Balani, of large size. Lastly, so restricted became its 

 supply of salt water, and so largely affected by the fresh waters of the 

 great rivers which flow into it, that its marine fauna had gradually 

 been killed off, or had become so dwarfed and malformed as to be 

 hardly recognizable.^ 



COI?,E.ESE'0]^TnDEITCE]. 



THE USE OF THE TEEM 'LATERITE'. 



Sir, — Since writing to you on the use of the term laterite^ two 

 papers have appeared that illustrate the confusion surrounding the 

 name at the present day. One of these is Mr. Mennell's " JN^ote on 

 Hhodesian Laterite " (Geol. Mag., August, 1909), and 1 shall be glad 

 if you will permit a few further remarks in connexion with it. 



Mr. Mennell agrees with Dr. Maclaren in considering that an 

 essential condition to the formation of laterite is the alternation of 

 perfectly distinct wet and dry seasons ; in fact, Mr. Mennell says that 

 this is the essential condition. Now, although throughout the 

 Federated Malay States the rock called ' laterite ' by engineers is, as 

 far as I am aware, ironstone deposited in weathered rocks, there is 

 in the State of Malacca an occurrence of rock that agrees with 

 Dr. Francis Buchanan's definition of laterite ; and in that it can be 

 dressed with an axe, and hardens on exposure to the atmosphere, has 

 proved of great utility in buildings, as can be seen in the old Portuguese 

 church that crowns the hill in Malacca Towu. This Malacca rock 

 would, I believe, be accepted by all as laterite, and carries with it the 

 idea of ' brick ', on which the name was founded. 



When Dr. Maclaren's paper appeared in 1906 I was struck by his 

 remark on the necessity of alternating wet and dry seasons, since my 

 impression was that no such alternation exists in Malacca ; and when 

 I saw the point emphasized by Mr. Mennell, I wrote to the Medical 

 Officer in Malacca asking for the figures of monthly rainfall for any 



1 See H. H. Howorth, "The Eecent Geological History of the Baltic" : Geol. 

 Mag., 1905, pp. 311, 337, 407, 454, 550. 



