398 Eighth Memoir on the [No. 137. 



To those, however, who are not fully acquainted with the subject, I 

 may say, that the " storm wave" is a mass of water of greater or less dia- 

 meter according to the storm, raised above the usual level of the ocean 

 by the diminished atmospheric pressure and perhaps other causes, and 

 driven bodily along with the storm or before it, and when it reaches 

 bays or river mouths, or other confined situations, causing by its fur- 

 ther rise when contracting, dreadful inundations ; but upon open coasts 

 rarely so, or not in so great a degree, as it can there spread out quickly 

 and find its level.* The " storm current" may be briefly described as 

 circular streams on the circumferences of rotatory storms, and of 

 this also we have evidence enough for the mariner at all times to 

 admit, and be on his guard against the possibility of, or even the great 

 probability of, them. 



We have thus in every storm two sets of forces (currents) independ- 

 ent of that of the wind, acting upon a ship ; the one carrying her 

 bodily onward on the track of the storm, and the other drifting her 

 round the periphery of that part of the storm circle in which she 

 may be. 



Taking, as the simplest case, and one nearly that of Madras Roads, 

 a storm travelling from East to West, and striking upon a Coast 

 running North and South, its centre passing over Pondicherry, we 

 should have then, for all ships in the ofling, one current, f the storm 

 wave" carrying them directly on shore, with greater or less velocity, 

 as they were nearer or farther from the centre ; and other currents, 

 " the storm currents" varying in their direction according to the situ- 

 ation of each ship in the storm circle, but always agreeing pretty nearly 

 with the direction of the wind. 



The current of the storm wave then is setting due West, but that 

 of the storm current West on the North side of the storm circle, 

 and due East at its South side; South at its Western edge, and 

 North at its Eastern side, and so on in ail the intermediate directions ; 

 and a ship putting to sea from Madras roads in our supposed case, 

 will be carried right towards the shore by the storm wave, and to 

 the S. Westward also by the storm current ; but if putting to sea from 



* The deep sea wave also, (the Jlot defond of the French writers) no doubt assists 

 the inundation ; but as this is not a surface cause, I do not allude to it. 



