Dr Robertson on the Tides of the Mediterranean. 23*7 
That portion of the Adriatic in which the city of Venice is 
built, is separated from the rest of the Mediterranean by a nar- 
row embankment of land, stretching from the Italian coast 
within the mouths of the Po, and joining a small peninsula 
opposite, not far from Treviso through this embankment the 
openings to the Adriatic are shallow, narrow, and, with the ex- 
ception of that by Malomocco, are extremely dangerous and 
difficult. 
I apprehend there is a regularity of the tides in other parts 
of the Mediterranean, greater and more remarkable than what 
is observed to take place on the coasts of that sea, where it is 
open, and not intercepted by islands or headlands. Thus, 
Chateaubriand, in vol. i. p. 123 of his Travels, when speaking 
of his visit to the Pyraeus, in the Gulf of ^Egina, says, 
‘‘ M. Favel stopped in the curvature formed by a neck of land, 
to shew me a sepulchre excavated in the rock ; it is now without 
roof, and is upon a level with the sea. By the regular flowing 
and ebbing of the tide, it is alternately covered and left expos- 
ed by turns, full and empty.” During a transitory abode on 
the banks of the Lago di Guarda, I was fully persuaded that it 
is also subject to an elevation and depression of its waters, 
which seemed to me to recur regularly, and independently of 
the melting of the snows on the summits of the surrounding 
Alps, for I have seen the rise recur after sunset, and we know 
that all alpine rivers are fuller during the day, and in the sum- 
mer, than when the sun is off the horizon, or in the winter. 
In addition to these observations respecting the tides of the 
Mediterranean, I beg leave to offer what I have remarked re- 
specting the very luminous appearance of its waters on the 
slightest agitation, so frequently perceived after sunset, espe- 
cially during the warm season. By many people this has been 
supposed to be caused by certain minute luminous insects exist- 
ing in the water*, to the disengagement of phosphorus from 
the excrements, or remains of fishes that have died, and other 
putrid matters. By seamen, this luminous appearance from the 
slightest agitation, has been considered as generally the precur- 
sor of blowing weather, and I am persuaded from repeated ob- 
servation, that the remark is as correct as it is general. This 
* See our last Number, p, 217. Ed. 
VOL. I. NO. 2. OCTOBER 1819. R 
