44G FOURTH REPORT 1834. 



but more particularly on the canal of Martesana, in which the 

 approximation to the parabolic theory is very close. In allusion 

 to the fluidity of water he states, that from accurate experiments 

 which had been made on the inclination of the Lake of Como 

 towards its outlet, the sensibility was found to be 7:f3-V7T- 



The treatise of Tadini is followed by a valuable practical pa- 

 per on the measurement of running water, reduced to the pro- 

 vincial measures of Italy and according to an extensive para- 

 bolical table appended. 



Lastly, this volume contains papers by Masetti, on the Theory 

 and Practice of the different Instruments {tachimetri idraulici) 

 which have been invented for the purpose of measuring the 

 velocitj'^ of running water by Castelli, Guglielmini, Ceva, Grandi, 

 Pitot, Mann, Brouckner, Woltmann, Saverien, Ximenes, Lecchi, 

 Michelotti, Leslie, and Venturoli. He divides them into two 

 classes, floating and fixed instruments, and demonstrates, both 

 theoretically and practically, that the fixed instruments give 

 the surest results ; in general all of them indicated, in a greater 

 or less degree, the diminution of velocity towards the bottom. 

 Masetti's conclusions are, that, for measuring the velocity of the 

 surface of rivers, the floating instrument or balls of Castelli is 

 the simplest and best. Secondly, that of the fixed instruments, 

 the sliding rod of Bonati, and the pendulum of Guglielmini, 

 improved by Venturoli, are best. 



A second paper, by Masetti, is devoted to the examination of 

 the different states of running water through orifices and rect- 

 tangular channels, according to the parabolic tables of Prony 

 and Eytelwein, calculated for different latitudes. The author 

 quotes the experiments of Newton, Borda, Bossut, Dubuat, 

 Mariotte, Michelotti, Navier, Hachette, Venturoli, &c. 



Volume the third, contains a paper by Fossombroni on the 

 celebrated Val di Chiana, and the systems of Warping and 

 Drainage which have been practised in it at different periods. 

 This volume also contains papers by the same author on 

 the distribution of Alluvions, on the Draining the Pontine 

 Marshes, and on rendering the river Arno navigable by means 

 of Jetties and Contractions. 



Volume the fourth, contains several valuable papers on Canals, 

 by Lecchi, Ferrari, Bruschetti, and Parea, including the origi- 

 nal letters and reports concerning the early navigations and 

 canals of Italy. 



Volume the fifth, is principally occupied by a translation from 

 the French of Borgnis Sur les Machines Hydrauliqiies, and two 

 papers by Magistrini and Masetti on the action and reaction of 

 •water on hydraulic machines. 



