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HISTORY OK ENGINEERING.

Book I.

was accounted deserving of being ranked among the cultivated sciences. Among hiswritings that “ Della Natura do Kiumi,” published in 1697, obtained him the greatestcelebrity. It treats of the equilibrium of fluids, the origin of springs, the motion of runningwater, either falling perpendicularly or on an inclined plane, together with the consequencesof friction, the resistance ottered by the air, &c. ; of the beds of rivers, their breadth,width, and depth, as well as slope, the uniting of rivers, as well as their discharge into thesea, the consequence of increase after heavy rains, the supplying artificial canals, the drainageof wet lands, and the precautions that should be taken when the course of a river is alteredor shortened.

Gugliehnini, in this work, puts forth a variety of new suggestions well deserving theattention of all who profess hydraulic architecture. He devoted his life to the pursuit ofthe sciences : his naturally robust constitution yielded to over-excitement, and he died atthe age of fifty-four, in the year 1710.

Giovanni Poleni (Marchese) was born at Venice in the year 1683, and at an early age hedistinguished himself in the acquirements of the sciences, and was entrusted by the Venetianstate with the care of all the hydraulic works. Ilis eminence was admitted bv thosesovereigns whose territories were subject to inundations throughout Italy , and he was fre-quently selected as the arbitrator to decide upon the conflicting opinions which arose whena river running through one state did injury to another. All his decisions were given in amanner to satisfy, as well as to increase his reputation, and in 1719, we find him appointedto succeed Niccola Bernoulli in the chair of mathematics at Padua .

Poleni was one of the most celebrated writers on hydraulics; and his work, “ Del Motomisto dell* Acqua,” is highly interesting, although the subject, perhaps, had been ablytreated before by some of the Italian philosophers. He in this work, however, has someingenious ideas; he supposes the bed of a river to he a rectangular canal, and a per-pendicular section of it an orifice, and calls that dead water which is between the surfaceand a certain point, where all the fluid molecules are in equilibrium, which he supposes aregoverned by the same laws as solid bodies.

The water which is between this certain point and the bottom of the canal is called livingwater. And he further considers that the motion of the water which flows through theorifice is occasioned by the action which the living water acquires from its fall, and fromthe pressure exerted by the dead water, and thus that motion is produced by the mixedwaters.

Another of his essays is entitled “ Delle Pescaie o Cateratte dei lati convcrgente, &c.”in which are many valuable observations ; but his principal work was that which appearedin the year 1718, entitled “ De Castellis per qua; derivantur Fluviorum Acqua*.”

He died 1761, aged sixty-eight. #

Eustuchio Manfredi , was born at Bologna in the year 167-1, and died in 1739 ; hepublished some valuable remarks in an edition of the works of Guglielmini on Rivers , alsoanother entitled “ Opere Idraulieke,” which relates chiefly to the opinions of the variousengineers upon the proposed change in the course of the Po and the Rheno.

Manfredi was appointed by the Bolognese in 1704 their chief engineer, was equallyeminent with his predecessor Guglielmini, whom he succeeded.

Bernardo ZendrinU was born near Breccia in 1679, and died in 1747 ; received hisinstructions under Dominico Guglielmini at the university of Padua , where he becamelearned in mathematics, astronomy, and medicine, which latter he practised for some timeas a profession: among his first scientific treatises was one on the hurricane which happenedat Venice in 1708, in which he enters upon the weight and electricity of the air ; the originand varieties of gas; the cause of wind, &c. lie then excited public attention by hisanalysis of a problem which still continues to present extreme difficulties, — if a fluid inmotion is confined within a given channel, the sides of which are susceptible of erosion,their surface will take the form suitable to the establishment of the resistance and the erosivepower of the fluid; this depends on the relation between the rapidity of the molecules andthe nature of the material that compose the sides. A curved surface is the usual form theyacquire; and the hypothesis of the transverse section being polygonal, with a flat bed andsloping sides, he says is not that which nature carves out. To have regard to the rapidityof fluid threads which traverse this section, it must not be supposed that they augmentfrom the bottom to the surface, where they would attain their maximum force; they onthe contrary augment from the entire surface as well as the sides, to a thread situatedsomewhere in the interior of the fluid mass, the position of which depends on its form andother circumstances. A memoir upon this subject was published in 1715, entitled “ Mododo ritrovare ne’ Fiumi la Linea di Corrosione.” It contains a description of a very simpleinstrument to ascertain the various rapidity of the current. The plains which lie betweenthe towns of Bologna and Ferrara being at this time inundated by the Reno, the inhabi-tants of Bologna wished to change the mouth of the river to beyond Ferrara into the F<>of Lombardy , and the most celebrated Italian engineers, Castelli Guglielmini, Gabrieland Eustachio Manfredi , supported them in their views in opposition to the inhabitants of