New Method of Navigating Vejfels. jo^ 



each half turn the force of the water overcomes the refinance 

 of the air, in the proportion of a thoufand to one ; but if the 

 wheel with its immoveable cogs were entirely immerfed ia 

 a current of water, it is evident that it would not turn at all, 

 becaufe the water would make two efforts in oppofite direc- 

 tions on the upper and lower cogs. If we now fuppofe fu^li 

 a cogged wheel totally immerfed in ftagnant water, and tliat 

 by means of any power it is made to turn on iti'df, it will 

 only agitate the water without producing a current; and if 

 it be free to advance or recede, it will do neither. But if 

 the cogs are rendered moveable by M. Danzel's method, in 

 fuch a manner that the wheel prefents alternately at each half 

 turn the flat fide and the edge, it will neceflarily advance, and 

 «c«afion a current of water behind it. 



NAVIGATION. 



M. Danzel has invented alfo an hydraulic 'machine fi»r 

 making a {hip or boat advance during a calm, ami e^vn 

 againft a current. The metfhanifm of this macliinc is ex- 

 tremely fimple; and if we did not know that tlie fimp'eft 

 means are often difcovercd the latefr, we might be furprifedl 

 that it fhould not have been found out before. It con- 

 lifts of a long pole, to the anterior extremity of v,hich an 

 apparatus, fhaped like a drawer without back or front, is 

 attached in fuch a manner that when puflied forwards it 

 folds itfelf back under the pole, to which it as it wci-e ad- 

 heres, and prelents to the water the thin cutting furface ol 

 its three edges, viz. of the bottom and two fides, which can 

 neither oppofe to the water a rofillance capable of prcventiuj 

 the pole from penetrating farther, or of making the fliip 

 recede. 



When the pole, w Inch is puflied forwards from the veflel, 

 lias attained to its full reach, the drawer as foon as the \x>\e 

 is pulled back afliimes a vertical pofition, and prefents to the 

 water its whole cavity. By thefe means it embraces a colunjn 

 of water, w hich, without finding means to cfcapc, prefles on 

 7 a. fur» 



