Notices rrj peeling Ntzu Books, 7/. 



for- boring, cannon to work both, horizontally aqcj ver.tipa 

 the whole apparatus belonging to them, and the method oi. 

 improving them. The detailed defciiptions whieh the author 

 gives of all thefe machines, conftructed under his own in- 

 spection, are illuftratcd by accurate engravings, to each of 

 which a proper feale is added. Mod of the plates were en- 

 graved from drawings executed under his own eye, or by Lis 

 ions. The invention, delineation, and conftruetion'of a flee' 

 hammer of cut granite, belongs, however, exclufively to his 

 younger fon, who was appointed by the College of Mines to 

 lupply his father's place during his long illnefs. The draw- 

 ings refpecting dams and dykes are by Mr, Nordwall, who, 

 has invented a new and advantageous method of conftrueling 

 canals of cut granite for hammer- works. 



The theoretic part, announced alfo as above, is the work 

 of Mr. Nordwall, and was not publifhed till 1800. The ex- 

 periments made on a filial 1 fcale, in regard to the motion and 

 power of water, are not fufficient for eftablifhing a general 

 theory, as it is not yet known with certainty what refults 

 would be given by experiments on a large fcale. For efla- 

 blifhing the theory of the action of water on water r wheels, 

 a peculiar machine was invented by the late Polhem, the 

 object of which was to determine the power of water accord- 

 ing to the different heights from which it falls, the bed me- 

 thod of conftructingfioat-boards, and to determine according to 

 the different depths the fize of the troughs. Some experiments 

 made on this fubject by the late Wallerius may be found In 

 Triewald's Lectures on Natural Philofophy, in Elvius'sTrea- 

 tife on the Action of the impelling Power of Water, and here 

 and there in the papers of the Academy of Sciences at Stock- 

 holm. In the years 1752 and 1753 the late ingenious Mr. 

 Smeaton made fimilar experiments, which were publifhed ia 

 1794 under the following title : Experimental Inquiry con- 

 cerning the natural Powers of Wind and Water to turn 

 Mills and other Machines. Some newer experiments have 

 been given by the abbe Bcflut in his excellent work on Hv- 

 drodynamics. By all thefe, however, the fubject has not 

 been illufirated fo fully as its importance and extent required. 

 It has been found, indeed, by experiment, that the moving 

 momentum of the power of water is very djflercnt according 

 to the nature of the wheels driven bv it, the more or lefs 

 oblique fituation of the troughs, the different pofition oFthe 

 float-boards, and their diftance from each other; but it' has 

 never yet been fufficiently examined what variations may be 

 produced by the different prciTure of the water in the though- 

 ihe different forms aud conftru&bn of the *fi :Tin 



ifhol. 



