59 8 Mr, mann’s 'freatife 
Rouen, vice-archite£t of the French navy, which gained 
the prize of the Royal Academy of Sciences and Belles 
Lettres of Mantua, for having givjen the beft folution of 
a problem propofed by that Society in 1776, in the fol- 
lowing terms : “ To indicate the bejl and cheapejl method 
“ of freeing navigable canals from banks of /and and 
“ earth formed in their beds which render them too Jhal- 
“ low .” This piece, printed at Mantua, by Pazzoni, in 
1778, contains lixty-three pages in quarto, and is di- 
vided into two parts; the firft contains the means of 
preventing the formation of banks in navigable canals; 
and the fecond offers divers methods for remedying 
them when they are already formed. For this purpofe 
the author propofes fix different machines of his ow r n 
invention : the firft may be employed in rivers near the 
fea, and fubjedt to the ebb and flow of the tides ; the fe- 
cond may be ufed in thofe where the waters are always 
nearly of the fame height and velocity ; the third and 
fourth are to be ufed in thofe places where the violence of 
the currents corrode the beds ; and the two lafl ferve to 
break up the banks of fand or earth formed in the bot- 
tom, and to carry off all heterogeneous bodies funk in 
the river, which caufe an obftacle to the current. It 
would be difficult to give a juft idea of thefe machines 
without the help of the fix plates which accompany the 
piece; 
