486 FOURTH REPORT 1834. 



sections of rivers assimilate in their inclination and magnitude, 

 and demonstrate the law of their augmentation in volume, but 

 decrease of velocity, as they approach the sea. 



It is the office of science to unravel these mysteries ; but al- 

 though the attention of philosophers has been directed to the 

 attainment of a true theory from the time of Galileo to the pre- 

 sent, our knowledge of the laws which govern the motion of 

 rivers is as yet very imperfect. The little success with which 

 they have been investigated may be attributed to the difficulty 

 of making correct observations, and to the local obstructions 

 which generally exist in most rivers ; and until we can ascertain 

 these points correctly, by means of a series of careful experi- 

 ments, we can only arrive at approximate results. 



The application of the science of hydraulics to rivers may 

 be justly said to have arisen in Italy. The peculiar physical 

 structure of the surface of that country was well calculated to 

 produce such a result, as it is intersected in all directions by 

 mountains, and by numerous torrents and rivers, which carry 

 off the superJBiuous waters to the Mediterranean and Adriatic 

 seas, on either side of the Peninsula. But the lofty character 

 of these mountains, as compared with the small extent of the 

 country through which the rivers have to run, causes them to 

 descend with extreme rapidity into the plains, which are fre- 

 quently ravaged and desolated to an extent unknown in wider 

 expanses of country. The evils thus generated, independently 

 of the litigation and strife which they occasioned (and which 

 exist at the present day), could hardly fail to excite the atten- 

 tion of ingenious men at an early period ; hence may be dated 

 the origin of that science which has since made such brilliant 

 progress in Italy. 



The arts of irrigation and drainage had been long known and 

 practised by the ancients; but whatever science existed, seems to 

 have remained dormant until the eleventh and twelfth centuries, 

 when the Italians applied themselves to render several of their 

 rivers navigable, such as the Brenta, the Mincio, the Arno, the 

 Reno, the Tecino, the Adda, &c., also several canals for irriga- 

 tion and drainage, such as the Muzza and others. But it was 

 only after the invention of the lock * for transporting vessels 



* Zendrini in his treatise, chap. 12, No. 20, speaking of the invention of the 

 lock says, " Ho trovato dunque che Dionisio e Pietro Domenico, fratelli da Vi- 

 terbo de fu Maestro Francesco di detta citta, ingegnere della Signoria di Vene- 

 zia, acquistano del 1481 li S di Settembreda Signori Contarini certo sito nella 

 Bastia di Stra, luogo ben note verso Padova, per formare in esso un soratore del 

 Piovego, che e quel canale, che viene da Padova al detto luogo di Stra ; ed in 

 carta supplica de'medesimi da Viterbo di detto anno resta espresso, ch'essi, che 



