APPENDIX. 
xvii 
REMARKS ON THE NAVAL AFFAIRS OF THE ANCIENTS, AND THE 
RATES OF SAILING OF THEIR VESSELS AT DIFFERENT PERIODS. 
The Greater Syrtis appears to have been at all times ill provided with 
ports and harbours, and may at the present day be considered to be 
wholly unprovided with any ; that is to say, with any which could 
be used as such by ships of modern construction. It will be 
observed that the whole line of coast laid down in the chart is, at 
the same time, very indifferently formed by nature to afford security 
to vessels of any description. 
It was not, however, necessary that the ports of the ancients 
should possess wholly by nature those local advantages which are 
at the present day considered to be essential for affording protec- 
tion ; and we find that many of them existed in places which must 
always have been unqualified by their position for affording the 
security required. In such places art was made to supply the defi- 
ciencies of nature, and harbours were built where none could other- 
wise have been obtained. The mode of constructing these artificial 
ports has been clearly defined by Vitruvius ; and as it may serve to 
explain what we have stated with respect to the present state of the 
ports of Ptolemeta and Aspis, we shall submit the passage in ques- 
tion as we have extracted it from Wilkins’s translation. 
“ A spot was, if possible, selected, which had the advantage of 
some protection on one of its sides; and the want of a corresponding 
defence on the other side was supplied in the following manner : — 
rows of grooved beams were driven in the water, connected by oaken 
planks, and bound together by chains. The surface of the ground 
below the water was then levelled and consolidated by means of 
transtilli, and the space comprehended between the beams filled up 
with a composition of rough stone, and cement formed of sea-sand 
mixed with lime, in the proportion of two parts to one, which soon 
