Having given the Proposition, he adds some particulars, to illustrate the same, before he declares his judgment upon it. For he relateth, that there is but one way, after the division of the Waters, to pass to the _Mediterranean_, which is by a Rivolet, called _Fresqueil_, that is conjoyn'd with the _Aude_: But, to pass to the _Ocean_, there are three; One, by _Riege_, entring into the _Caronne_ above _Tholouse_; the other, by _Lers_, passing on the side, and below the same Town; and the third, by _Sor_, falling into the River _Agoust_ under _Castres_, afterwards into the _Tarne_, and thence to _Montauban_, and lastly into the _Garonne_. And that, to compass this design, all these Rivers and Rivolets are first to be made Navigable unto their _Sluces_; that of _Aude_ and _Fresqueil_ for the _Mediterranean_, and one of the others, such as shall be chosen, for the _Ocean_. He addeth, that, as to the several Ways passing to the _Ocean_, all of them commended as proper and convenient, and the three Countries concerned therein, speaking every one for their advantage: Those of _Castres_ and {42} _Montauban_, are for the River _Agoust_; those of _Tholouse_, for _Riege_; and the rest, for _Lers_. Now concerning his Opinion upon this Proposition, he thinks, that all that hath been represented touching this matter, can signifie very little, seeing that the main thing is wanting, which is the assurance, and certain and positive mensuration of the height and quantity of the Waters, necessary to fall into both the Channels of the _Aude_ and _Caronne_: that there must be plenty of that, to furnish at all times and alwayes the highest and first _sluces_, since what once issues thence, doth never enter again into them; and after some Boats are passed, if there should not be a sufficient supply for those that come after; either to go up, or to go down, all would stand dry, and Merchants and their commodities would stay long enough expecting the supply of Rains, to their great detriment. He concludeth therefore, that no knowing and discreet Person is able, in matters of this nature, to give a positive answer, without having before him a large and exact Topographical Map of those places, and of the sources of all the Rivolets, that are to supply the Water to the Head of the pretended Channel, together with a full account of the survey and mensuration of all the places, through which it is to pass; of the Nature of the Ground, whether it be stony, sandy, rocky, &c. of the exact level of all the places, where it is to be made, and of the several risings and depressions thereof, to be assured that the Water may be conveyed to the greatest rising, and to the highest _Sluce_; and lastly, of the quantity, that may be had at high, middle, and low Water, to have enough for all times; that all these things being first made out, 'tis then time enough to judge of the possibility of the thing, and to calculate the charges necessary for Execution.