TEREDO. 147 



1731, 1770, 1827, 1858, and 1859. Very little rain fell 

 in those years. Laurent showed that they are suffocated 

 and destroyed by oil being poured on the water in a 

 vessel containing Teredines in a piece of wood. He also 

 proved that they could not liA^e in the " Salines ^^ at 

 Hieres, too much salt being as injurious to them as 

 fi'csh water. But it appears that certain species 

 live in bracldsh or even fresh water. The T. Sene- 

 galensis of De Blainville was discovered by Adanson 

 in the roots of the mangrove and another kind 

 of tree lining the banks of the Niger, Gambler, and 

 other rivers on the west coast of Africa, which were 

 only subject to an influx of sea-water for a few months 

 in each year. According to Adanson the water of these 

 rivers is quite fresh or sweet during the remaining 

 months ; and T. Senegalensis not only exists, but re- 

 tains its full vigour throughout the whole year. This 

 statement, however, must be received with some quali- 

 fication. I am told by Dr. Welwitsch, the great botani- 

 cal traveller, that in the tidal rivers of South Africa the 

 water in the middle of the stream is fresh, while that 

 on the sides is brackish, and that no kind of mangrove 

 has been known to live in fresh water. Another sort of 

 shipworm {Nausitora Dunlopei of Perceval Wright) 

 has been lately found in India, inhabiting the river 

 Comer, one of the branches of the Ganges, and a per- 

 fectly freshwater stream, that returns to the main river 

 at a distance of about 70 miles from the sea. Dr. Kirk, 

 the friend and companion of Livingstone, informs me 

 that he picked up a piece of ebony [DaJbergia me- 

 lanoooylon) on a sandbank in the Zambesi river, the 

 water of which was there always fresh and drink- 

 able, 100 miles from the sea — very far beyond the in- 

 fluence of the tide, which never comes above 10 miles 



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