86 ' Correspondence. 



yet dispense witli a voluminous categorical list of stones — as con- 

 Teying no sense at all commensurate with the labour and the in- 

 evitable indistinctness attending such niceties of specific distinctions 

 — it is all the more essential that our type-names and the terminology 

 ■we apply to important characteristics should be well understood and 

 carefully used. We are often told to practise what we preach : in 

 matters of science, at least, we may adopt the easier and safer maxim 

 to teach what we practise. 



Yours truly, 



Henbt B. Medlicott, 

 Greological Survey of India, Calcutta. 

 Chota, Nagpore, December 1, 1866. 



INUNDATIONS AND THEIR PEEVENTION. 



To the Editor of the Geological Magazine. 



Sib, — Under this heading a writer in the Pall Mall Gazette, who 

 signs himself X, recommends the construction of " artificial lakes " or 

 "huge reservoirs " on each side of the Pennine chain, " which would 

 have the effect of preventing inundations like those of last month in 

 Leeds, York, Salford, etc." X gives this idea as an origination of his 

 own. It is, however, EUet's idea, and it was published for him by 

 the United States Government, in a book of some 400 pages, in 1853. 

 The book is entitled, "The Mississippi and the Ohio rivers, containing 

 plans for the protection of the delta from inundation." The prin- 

 ciples of tills book are discussed in the last chapter of " Eain and 

 Eivers," which is entitled "EUet on the Mississippi." In reference 

 to the late floods in France, X says, "In 1856 the Emperor addressed 

 a letter to the Minister of the Interior on this subject, in which he 

 pointed out that the first object was to ascertain the cause of these 

 sudden floods, and suggested that they came from the rainfall among 

 the mountains." And again, " Our experience in England seems to 

 confirm the Emperor's theory that certain floods are chiefly caused 

 by rain in mountainous districts." The Emperor's theory is as cer- 

 tainly true, and one would have thought as self-evident as that two 

 and two, make four. And posterity will find it difficult to believe 

 that in the 19th century such a truism could have been enunciated as 

 a discovery! This so-thought discovery, however, is a most important 

 step taken in advance when we consider the profound ignorance 

 which prevails on the subject. And it will be of advantage to the 

 entire world that the most enlightened, clear-headed, and energetic 

 of its sovereigns has learned the first great A in the Hornbook of 

 Eain and Eivers. Nor is it of slight importance that the Pall Mall 

 megatherium has changed the tone of his roaring, and has taken to 

 steal, and to promulgate as his own, doctrines, which he only yester- 

 day attempted to controvert. He at least has the power to fuhlish 

 those stolen doctrines. His own idea on alluviums was that they were 

 hatched out of igneous "nest-eggs," {sic) and it is really quite " a nice 

 change " when X finds that aqueous causes noio can " cover the pro- 

 ductive soil several feet deep by stones, etc.," and proves that aqueous 



