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case tlie light appears to suffuse the whole surface of the 
water; hut it is necessary to distinguish between this and 
another phase, in which the light is visible only in isolated 
patches, having no connection with one another, and where 
the liquid itself presents no appearance of luminosity : the 
latter we shall denominate partial phosphorescence. 
The first mode of phosphorescence is visible in almost every 
part of the Mediterranean Sea. On the shores of the ocean it 
has been observed at Havre, Dieppe, Ostend, and doubtless in 
ah seaports and tranquil basins. I have myself noticed it at 
La Rochelle, Boulogne, &c. ; but it was at the place last- 
named that I studied it with the closest attention. Here the 
phosphorescence, which is very conspicuous in the “ port/’ 
properly so called, in the dry-dock, and especially at the oyster- 
beds,* becomes less perceptible between the two jetties, and 
entirely disappears where the fresh waters of the Liane inter- 
mingle with those of the sea. 
The following are some of the observations made by me in 
the locality just named, and which being, so to speak, the 
highway between France and England, will doubtless be well 
known to many of the readers of this Journal. 
However favourable the circumstances may otherwise have 
been for the production of the phenomenon, perfectly tran- 
quil water was always completely dark. A concussion, no 
matter how feeble, was requisite for the manifestation of fight. 
A grain of sand thrown upon the dark surface gave rise to 
a luminous blot, and the undulations proceeding from this 
centre were perceptible as luminous circles, becoming larger 
and larger, but at the same time more and more faint in 
proportion to their distance; just as the concentric undu- 
lations themselves became more feeble as they receded from 
the centre. A stone as large as one’s fist produced similar 
effects, but in a more marked degree ; and then, moreover, the 
drops resulting from the splash resembled the sparks flying 
from an anvil on which the blacksmith is welding a bar of iron 
raised to a white heat. Tranquillity being again restored to the 
surface, all returns to obscurity, and the keenest observer 
could detect nothing that would lead him to suppose that this 
water, dark even to blackness, was ready at any moment to 
burst into coruscations, and recognize by its phosphorescent 
play, the descent upon its surface even of the minutest frag- 
ment of straw. The oyster-bed was always encircled by a 
phosphorescent belt, arising from the constant undulations of 
the sea, which broke upon the beach in gentle ripples. Seen 
from a distance, these little waves, barely four inches in height, 
* According to the project, recently adopted, for the excavation of a wet- 
dock, the oyster-beds will disappear : perhaps they are no longer in existence. 
