more or less subject, render strong precautions, and the most unremitting vigilance, essentially necessary to the preservation of the property and the lives of the inhabitants. None of these objects have been overlooked by the ingenious Piedmontese; no small proportion of whom are indebted for their support to the increased means of subsistence, arising from inland navigation, manufactures, and the universal practice of irrigation. It is scarcely to be supposed, however, that the uncombined and unassisted efforts of individuals, or of small communities, should draw from these sources all the benefits which they are capable of affording. Petty jealousies, clashing interests, and insufficiency of capital, would frequently prove obstacles to the execution of plans of acknowleged utility; while some works would be improperly undertaken, and more still would be injudiciously neglected, without the assistance of able engineers, who combine a perfect knowlege of the principles of their profession with the most correct local information.

Emanuel the third, with the view of remedying some of these inconveniencies, instituted in the year 1760, in the vicinity of Turin, an hydraulic school; which, with due allowance for the disadvantages usually attending the infancy of an establishment of this nature, promised to be productive of considerable benefit to the community. Many extensive works, projected by MICHELOTTI and divers engineers, were actually carried into execution; and others not less important were suspended or interrupted by the events of the late disastrous war. The valuable mass of information on all these points, which the professional pursuits of the author of the work before us, and of his father and brother, had enabled them to collect, first suggested the idea of a full and correct description of the course and phænomena of the rivers of Piedmont, and of the various uses to which their waters are and might be applied. A plan embracing fuch a wide field, and at the same time requiring such accuracy in the details, appeared, however, an object so important, and its completion by an individual seemed an undertaking so arduous, that the author resolved previously to try the sense of the public, by the present volume, which, under the modest title of an Essay, discloses the outline of the important work to which it is designed as a prelude. We sincerely trust that he will not be deterred from his first purpose. The publication now on our table induces us to form the most favourable opinion of his talents and information; and the ori ginality of the plan will suggest a strong claim to indulgence, for any deficiences and irregularities in the execution of it.

The work commences with pointing out the sources of the rivers of Piedmont, under the different chains of mountains

which almost encircle the valley of the Po. After a few interesting observations on the principal phænomena which these mountains present, the author proceeds to examine the nature and origin of the various substances which are carried down by the rivers. Here, in particular, he appears to be fully master of his subject; and though his reasonings pre-suppose no inconsiderable acquaintance with chemistry and geology, he carefully abstains from introducing any matter not immediately necessary to his purpose: on all occasions chusing rather to refer his readers to such authorities as they would most probably have an opportunity of consulting.

Chapter II describes the character and most usual appearances of the Piedmontese rivers. Passing slightly over those features which are common to rivers in general, M. MICHELOTTI chiefly directs the attention of philosophers to the great floods to which we have before alluded. To give some idea of their violence, it is stated that at Turin the Po often flows at the prodigious rate of fifteen or eighteen English miles per hour; and, as some of the larger rivers, which it receives. above Turin, remain navigable at all periods, it follows that this impetus must have been almost wholly communicated by a few smaller streams, the rapidity of which must in course greatly exceed the ascertained velocity of the Po. Accordingly, it is affirmed by the neighbouring peasants, that, at these periods, stones are dashed against each other with such force as to strike fire in the stream. Many pieces of two or three hundred weight are thrown on the banks; and others, carried by the stream against the side of the channel, shake the ground to a considerable distance. The greatest innundations are observed to take place when the rainy season is accompanied by a south wind, a more active agent in dissolving the snow of the glaciers than the most intense rays of the sun: but probably the operation of both these causes is materially strengthened and concentrated by another circumstance, to which the author does not appear to have paid sufficient attention. The fall in these rivers being very considerable, the body of water which they usually contain must form to itself a narrow current; and consequently an accession of water, in the same proportion as would but slightly accelerate the course of the broad rivers of more level districts, must seek to discharge itself from these narrow channels in torrents and inundations. The chapter concludes with remarks on the gold found in the sands of several rivers, and an enumeration of the trees and shrubs commonly planted for the defence of the banks.

The third chapter contains a short description of the course of the different rivers of Piedmont, and the principal canals APP. REV. VOL. LI.

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which proceed from them. This enumeration commences with the Toce, a small river which, rising on the confines of the Valais, meets the Po just before it leaves the Piedmontese territory. The author then proceeds to describe all the streams which join the left bank of the Po; and after having stated the course of that river also, from its source to its entry into the Milanese territory, he in the same manner follows its right bank, concluding with the Trebbia: only a part of the course of which is detailed, because it leaves the Sardinian dominions long before it reaches the Po. Much light is, no doubt, thrown on the topography of Piedmont by this part of the work: but M. MICHELOTTI adheres so strictly to his intention of exhibiting a mere outline, that it is little calculated to interest foreigners. The Dota Riparia, probably on account of its vicinity to the metropolis, is described in greater detail. Four plates, neatly engraved by Cipriani, represent its course from Susa to Turin; and a copious index explains the various canals, sluices, bridges, and mills connected with the Dora. From the minuteness of this part of the essay, it seems not unfair to suppose that it was intended as a specimen of the author's projected undertaking.

In the first chapter, (he says) it was observed that the Dora Ri. paria rises on the confines of Dauphiné and Piedmont. After having washed the walls of Susa. it leaves the mountains between the hill of Musiné, and that which is crowned by the antient Sanctuary of St. Michael. Among the smaller tributary streams, we remark the Cinischia, or Cinicella, which, descending from Mount Cenis, known to the antients under the name of Mons Cinerum, meets the left bank of the Dora, about a quarter of a mile from a suburb of Susa, called St. Giacomo. Also on the left, but nearer to the city, it receives the Merdarello. The former carries down a vast quantity of very small ash-coloured sand, which renders any increase in its waters discernible as far as Turin. The city of Susa is supplied with water from the Dora: but this stream, as well as others, which it throws out above, is too small to arrest our attention. The first after these is the canal of Forest, (A. plate IV.) which is the most considerable of any that issue from the left bank of the river. Nos. 127, 128, 129, denote three smaller openings. The first of these four streams turns several mills, of various descriptions; after which it is applied, like the rest, to the purpose of irrigation. B marks the entrance of the second canal, or Roggia di Bossoleno; and on the left at C are two others of equal size, and at a little distance from each other. The fourth opening at D, also on the left, gives rise to the canal of Chianocco. The fifth canal, at E, passes through the hills, which overhang the right bank of the Dora, in the territory of St. Giorio. The sixth opening in the territory of St. Antonio is also on the right. This canal differs from those already mentioned, in having at its entrance a dyke or wear across the river, to conduct the

water.

water. It is a stream of considerable importance, turning several mills, and irrigating the extensive districts of Vajes and La Chiusa ; and it falls at last into the canal of Rivoli, whereas all the preceding return sooner or later into the river. The canal of Rivoli, proceeding from the point G, also on the right, is considerably larger than the last mentioned, and may be calculated at ten ruote* of water in the summer It is afterward increased by the accession of a smaller stream, which issues at No. 125, and waters a small tract of land. The eighth canal of importance is taken from the point H, for the benefit of the districts of Casellette and Alpignano, in the plains of which it spreads and loses itself, without again returning to the Dora. Neither this canal nor that of Rivoli is provided with any wear across the river; and it is asserted that most of those which now exist are of very modern construction, there being reason to believe that the bed of the river has sunk in many places. The ninth opening, at No. 124, supplies the canal of Avigliano; and here the instability of the soil makes it necessary to vary at times the position of the wear. This stream, after having worked mills of various descriptions, divides into smaller branches, which water the districts of St. Ambrogio, Avigliano, and Buttigliera, and at last it falls into the tenth, or canal of the mills of Buttigliera, which leaves the river at No. 117.

The eleventh opening, at No. 112 on the right, supplies the canal of Grugliasco, which, winding many miles through the plains, waters a considerable extent of country, and turns several mills. At No. 109 it passes under rocks; and these subterraneous excavations, which are by no means unusual, are in those districts called Cats, (Gatti,) a term not altogether inappropriate, if we consider the unpleasant and aukward postures which the workmen are obliged to assume, when employed in repairing or cleaning out the canal. The twelfth opening, at No. 107, supplies the mills and other works of Alpignano; after which, with the accession of some smaller streams, it forms the canal Becca, or Becchia, which extends its benefits as far as part of the district of Turin. The thirteenth, on the left of the river, at No. 10, supplies the canal Consorzia; .which, after being carried across the Dora by an aqueduct, turns several mills, and then branches into subdivisions, for the purpose of irrigation. The fourteenth, issuing at No. 95, immediately below the bridge of Alpignano, sup plies the canal of Pianezza, also to the left of the river fifteenth, on the left, (plate I. 92.) supplies the canal of La Veneria Real, which works several mills and irrigates plains of vast extent. The sixteenth, on the right, waters the fields of Rivoli. The seventeenth, opening at No. 79, supplies the canal of Collegno; and the eighteenth, at No. 75, that at Druent. Both these are on the left of the river, and, in their numerous subdivisions, work many mills of various descriptions, and water extensive plains. The nineteenth, at No. 71, merely supplies the mills, &c. of an individual, who has a right to a stream thrown off by a wear. The twentieth, on the left,

The

The Ruota, or Piedmontese square foot, equals 456,3289 inches, or about 2 square feet English.

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at

at No. 68, supplies the canal Putea, part of which crosses the river by an aqueduct attached to the bridge at Collegno, and reaches the plains of Turin. The twenty-first, on the left, at No. 52, supplies the manor of Collegno, and various works belonging to the Lord. The twenty-second, on the right, supplies the canal Cossola, which, as well as those last mentioned, is provided with a wear. The twentythird, at No. 48, supplies what is called the new canal. The twenty-fourth, at No. 44, supplies the old canal, or canal of Lucent. The twenty fifth, at No. 39, which is the first within the district of Turin, supplies the numerous mills and manufactures of this city, besides several royal works. Its various ramifications may be seen in the plate and index. Lastly, the twenty-sixth, at No. 30, called the new royal canal, supplies a great variety of works, particularly the manufactures in the Real Parco, and irrigates a considerable district.

We have purposely avoided repeating many particulars inserted in the index attached to the plates, which appears to specify as many objects as the nature of our plan required. It is easy to conceive on how large a scale it would have been necessary to construct the plates, had we engaged in minute details respecting the course of the different canals, and the numerous small streams which the Dora receives in its progress. Still less was it our intention to enter into those details which belong particularly to hydraulic archi

tecture.

The course of the Dora in the mountains, from its source to the city of Susa, may be computed at 20 or 23 British miles, and from Susa, till it meets the Po, nearly 66. The fish of this river are scarce and in little esteem.'

Chapter IV contains reflections on some of the means of extending the advantages derived from the rivers of Piedmont; principally relating to the navigation of the Po and Tanaro, which appears in all seasons to be difficult, and not unfrequently extremely hazardous. After the floods, the Po, instead of retiring into one channel, forms itself into several small branches; and notwithstanding the appointment of a Capitano della Navigazione, a principal part of whose office it is to determine what course the bargemen are to take, it often happens that, through ignorance or carelessness, they are in danger of running aground, from the want of sufficient depth of water, or of dashing their little vessels against the trees and fragments of rocks brought down by the torrent. Unpleasant accidents are also occasioned by the dykes erected in the river, for the purpose of directing the current against the floating mills, which are common on the Po and the Tanaro, where the flatness of the neighbouring country renders mills of a different construction very rare. To obviate these inconveniences, the author generally recommends the formation of a navigable canal, nearly parallel with the course of the river. He still

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