280 



activity of the navigation. The heavier the 

 tonnage of ships, the less frequent will be their 

 passage. I dwell on these technical considera- 

 tions to remove the apprehension of wanting a 

 sufficient volume of water to feed a canal of 

 considerable length ; and if it be meant to serve 

 at the same time for small boats filled for in- 

 land trade, locks of less dimensions might be 

 added to the great locks, in order to ceconomize 

 the waters, which has been practised on the 

 Grand Junction canal, and was projected for 

 some time on the Caledonian canal *, 



» The capacity of the canal of Languedoc, or the prisme 

 de remplissage of the whole canal, is seven millions of cubic 

 inches, according to the calculations of M. Clauzade. The 

 annual expence of the locks, for 960 double passages of 

 boats, was 11 J millions m. c. This expence, caused by locks 

 somewhat too large for a very active given navigation, and 

 in small boats, is consequently to the capacity of the canal 

 as : 1. It requires besides, 3 J millions m. c, to re-esta- 

 blish the waters after the shutting up as far as Fresquel, and 

 that quantity of water is furnished in 9 days, by the upper 

 basin, or the artificial source. (Huernede Pommeuse, p. 256, 

 258, 265.) The product of the evaporation is estimated in 

 the canal, the reservoirs and the trenches, during 320 days 

 of navigation, 1,900,000 m. c. (Dueros Mem., p. 41.) In 

 comparing the Caledonian canal with that of Languedoc, I find 

 the surface of the sections as 5 to 1 ; and the length of the 

 parts dug in the canal, (excluding the navigable line of the 

 lakes of Scotland), as 1 : 6|. It results from these state- 

 ments, that the capacities of the two canals, one of which 

 bears flat- ribbed boats, of 100 to 120 tons, and the othec 



