VOL. VII.] PHILOSOPHICAL TRANSACTIONS. 725 



It was necessary to place these pipes so, that they might not take the water but 

 at about four fathoms high from the ground, because it is not possible to make 

 such a great collection of waters in this conservatory, especially of such waters 

 as come in part from snows and rains, without store of dirt, sand, stones, pieces 

 of wood from the neighbouring forests, and therefore there was an absolute 

 necessity to leave some space for all this stuff, to prevent obstructing or spoiling 

 the pipes. On which occasion it is to be added, that forasmuch as in length of 

 time this dirt may be heaped up to such a height as to stop up the pi{x;s; to 

 avoid this inconvenience, there has been made in the said square cavity, an 

 opening below, answering to the aqueduct; which opening is to be commonly 

 shut by a large iron-gate, that can be drawn up or opened at pleasure from the 

 gallery, that so the water finding this vent, and forcibly issuing, may carry with 

 it all the dirt, or other stuff that shall be gathered at the bottom of this store- 

 house. 



As to the grand basin, to which the waters of the store-house are by the 

 channel of St. Feriol to be conveyed, it may be added, that it is to be two fa- 

 thoms deep all over; that it receives the waters of the said channel at one of its 

 corners, and distributes them by two others, through two channels, into the 

 ocean and Mediterranean : that there are to be two other channels, one to dis- 

 charge the basin when there is too much water, the other is to come out of 

 the deriving channel, to make the dirty waters run out, that so the pond re- 

 ceiving no other but clear and clean waters, may not be filled up with mud. 



This basin is in a manner nearly finished. It is to have not only an elegant 

 key, but a regular town built round about it after the model of the Place Royal 

 of Paris; all the houses alike and equal, with great arches beneath, to go under 

 cover to the key. There is also to be an arsenal, for boats to lie under, and for 

 containing all necessaries to build and furnish them. 



This royal channel is every where 5 fathoms broad at the bottom, and for the 

 most part Q fathoms and 2 feet broad above. It is ordinarily between 6 and g 

 feet deep, and sometimes more. And as there is a considerable fall for about 

 ten Languedoc leagues, from the point of distribution, where it is highest, 

 unto its discharge into the Garonne, where it is very low, you descend and as- 

 cend by the means of 1 8 sluices, which at certain distances cut this channel, and 

 bear up the waters that are above. 



But as to the communication of this channel on the other side of the great 

 basin towards the Mediterranean, that will require more time: yet the work is 

 there begun, and the same order and rules will be observed on that side as on 

 the other, as well for the opening of the channels as the structure of the gates 

 and sluices. 



