HISTORY OF ENGINEERING.

Rook I.

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it abundant water to irrigate the lands of Piedmont, where this practice has been adoptedfrom time immemorial.

Near Bologna , Ferrara , and towards the Adriatic Sea , the land is often under water, andtin- inhabitants of this district are subject to breathe an impure and malignant air in con-sequence; this is chiefly owing to the attempts made in the middle ages to keep out thePo, by constantly throwing up dykes, for the purpose of penning back the water in theriver ; this naturally, in the course of years, from the deposit, tended to elevate the bed con-siderably above the country it flowed through.

At the mouth of the Po, vegetation flourished amidst these deposits and overflows, pro-ducing the worst kinds of malaria, and that portion of the coast of the Adriatic , whichintervenes between Mount Pesaro and the port of Brondolo, and which formerly exhibiteda deep hollow curve for its section, was by the alluvium elevated to a considerable height ;in consequence all the roads were rendered impassable, and the various streams whichflowed into the sea, at this portion of the coast, as the Po at Goro, the ancient Po ofPrimaro, the Lamone, the Ronio, the Savio, Usa , Marrechia, and many others, whichbrought down in their course a quantity of deposit, had their beds considerably elevated ;this occasioned the hanks which confined them to be raised in proportion, and when thesefrom neglect gave way, in the time of floods, the whole country became one vast lagune orswamp.

Ravenna contained upwards of 14,000 inhabitants, and was founded, according to Strabo ,by a colony of Thessalians, on the borders of the sea, from which it is now, in consequenceof the deposit from these rivers, more than two leagues distant, and that place, whichwas a port in the time of Augustus , and served him to assemble his fleet, is now land.Even so late as the time of Theodorie, it was a place of so much importance, that after hisconquest of Italy , he made it his capital, and highly embellished it; it contains his tomb,which is a curious structure of lstrian stone, 34 feet in diameter, covered by a singleblock, placed 40 feet above the floor; the lower part of this circular edifice is now filledwith water.

Ravenna was built, like ’Cenice, in the middle of the waters, and by the Romans it wasunited to the main land; it is now situated between the mouths of the ancient PoofPrimaro, of those of Lamone, of the Ronio, and of the Montone, and this once celebratedmarine establishment is now an extensive marsh.

The lagunes of Commachio once formed a portion of the sea; they are now situatedbetween the ancient beds of the Po of Primaro and of the Po of Yolano. When thetongue of land, or bank, which separates these lagunes from the sea was thrown up isnot known. Neglect during the middle ages of these great and important rivers was thechief cause of the changes which have taken place on this coast; their deposits have filledup the sea where they have discharged themselves: Ravenna is now 8000, Rimini 1500,and Adria 32,000 metres from the coast; and each of these places ranked as ports in thetime of the Romans.

Rimini was the spot on which the JEmilian and Flaminian roads terminated, and inthe time of Augustus it was a port of importance; here was his arch of triumph and hisbridge.

Cpwards of 160 square leagues of country was desolated by these overflowings of thevarious rivers in the sixteenth century, and it was a constant cause of dispute between theinhabitants of Bologna and those cf Ferrara.

In the twelfth century the Po had passed near Ferrara , and in 1155 it changed itscourse, and in the year 1600 it was deemed advisable to separate the Panaro and Rheno,which flowed over its ancient bed, called the Po di Primaro, and which inundated thevalleys of Commachio . About 1604, the Pope ordered that the Rheno should be turnedinto the valley of Santa Martina , but all that could be done could not prevent their beingoverflowed, for the banks gave way several times, and a very considerable sum of moneywas spent to no purpose. These terrible inundations alarmed the whole of the inhabitantsof t liis part of Italy ; the evils were daily increasing, and the most eminent scholars of theday, (for there were no engineers,).were consulted upon the occasion ; it may be consideredhighly fortunate for Europe and the world in general, that these disasters directed thelabours of the greatest philosophers of the age, when science began to revive, to the studyof hydraulic architecture: all we at present know has its origin in their experiments;all the useful inventions applicable to modern practice, we owe to the writings ofFrancesco Mengotti, Mario Lorgna, Pietro Zuliani, Francesco Focacci, Antonio Tandini,Isidoro Bernareggi, Barnabita, Giovambatista Masetti, Vittorio Fossombroni , Pietro Paoli,Antonio Lecchi, Bernardino Ferrari, Giuseppe Bruschetti, Carlo Perea, Eustachio Man-freili, Giovanni Poleri, Paolo Frisio, Tommaso Perelli, Giovanni Bacciali, Eustachio Zanotti , Ruggiero Bosvich, Leonardo Zimines, Bernardino Zendrini , Dominico Gugliel-mini, Galileo Galilei , Benedetto Castelli , Alfonso Borelli , Evangelista Torricelli , GuidoGrtindi, Famiano Mcchelini, Tommaso Narducci, Lorenzo Albozi, Geminano Mon-