1847.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



375 



shall now consider) — the former we might term exotic— the latter, as more 

 immediately the growth of Italy, national — marked and were identified 

 with the two distinct countries in which they originated. The modifications 

 and improvements of which these were susceptible, and the perfection to 

 which the latter was carried, prevented the city savouring of any degree of 

 monotony ; and, indeed, it is in the various phases of style and diversity of 

 character in this city of palaces — favoured as it is in this respect by the 

 views, the most tempting to the painter, which a labyrinth of serpentine 

 streets and canals continually present — which appeal with so much interest 

 to the historian, arehsologist, and artist ; and constitute the great charms 

 of the pictures of Canaletti. 



If the Italians exhibited, in their revived architecture, less of the passion 

 for the picturesque than their predecessors, they achieved grander results 

 than had been accomplished by them ; if in their works there was less 

 imagination — that is, less of a capricious kind — there was more reason ; if 

 less to win upon the feelings of the poet, there was more to satisfy the 

 individual whose views were moulded and shaped by regulation and rule ; — 

 but various causes prevent all analogy in the two cases ; their beauties and 

 defects are in no way referable to the same standard ; and hence it is we 

 entirely demur to that one-sided and partial observation which denies any 

 merit to exist in one style of architecture, because it differs from another : 

 we rather like to enjoy their separate beauties and features ; and allow, at 

 least, the existence of fitness, propriety, and every essential of beauty, in all 

 works, however opposite they may be in character, which are in harmony 

 with the tastes and requirements of the nations and times that produced 

 them. But we may remark, in a comparison of the Arabic with the Italian 

 styles, that whereas the former, by the manner of the division and multipli- 

 cation of the parts, produced a degree of variety that at first seemed almost 

 confusion ; in the latter, those parts being less minutely divided, fewer, and 

 larger, simplicity resulted ; before, it seemed scarcely as if they were under 

 the guidance of any sound canons or fixed principles, where the chief object 

 was to give the freest scope and play to the fancy: but, now, the precepts 

 and principles, as derived more immediately from a greater considering 

 intellect and a less indulging imagination, were stern, severe, and settled, — 

 the fancy being reined in — her movements restrained by the cooler dictates 

 of the understanding ; yet the influence of a favoured climate shed its ele- 

 gancy and refinement over the minds of the Italian artists, imbueing them 

 with that poetic feeling which made their works look noble, classic, and 

 stately — and far, very far, from cold or prosaic, though they might not 

 boast of the luxuriant profusion of their predecessors, the Moors and 

 Arabians. 



HYDRAULIC LOG. 



The common log is a simple apparatus, familiar to all who have been within 

 the view of the encirling horizon ; and, were its accuracy equal to its sim- 

 plicity, it would undoubtedly be a perfect instrument. Such, however, is 

 not the case, — hence various contrivances have been proposed : Massey's 

 l>atent log, and Cave's apparatus for indicating the speed of a vessel, are both 

 very ingenious contrivances, but apparently too complicated to answer the 

 purpose intended. The former will answer tolerably well within a limited 

 range of the speed to which the driving-cone is adjusted, but at any consider- 

 able variation from that speed its correctness is not to be depended on. 

 Perhaps, it may be said that the common log is sufficient for its purpose, 

 because it has never yet been superseded; true, it has not been superseded, 

 and why ? — because nothing has yet been introduced having the two necessary 

 qualities, simplicity and accuracy combined. I leave the question of the 

 sufficiency of the common log to those who have practical experience on the 

 matter, and who, I am sure, will appreciate an instrument which may at all 

 times be relied upon. And though it matters not much when the errors of 

 the common log can be corrected by observation, yet, when the state of the 

 weather and atmosphere for several days, or weeks, do not admit of observa- 

 tions being taken, it becomes a matter of great importance to know the 

 actual distance the vessel has traversed. 



The instrument I propose for this purpose' is free from mechanical com- 

 plexity, depending for its accuracy entirely upon the natural law and hydro- 

 dynamic property of fluids, and having some similarity to a common baro- 

 meter. 



A reference to the annexed diagram will explain the construction of the 



instrument. The figures are drawn to a scale of two inches to a foot. Fig 

 1, is a plan ; fig. 2, is a side elevation ; fig. 3, is an end elevation ; and fig" 

 4, is a broken section of the pipe /, and mouth-piece g. a a, is a frame oj 

 stand ; i, is a bracket, forming with the piece c, a universal joint d, is a 



glass tube having a bulb at its lower end for the purpose of holding mercury 

 and with which it should be rather more than half filled ; this tube must be 



firmly fixed in the piece c ; e,'\% another glass tube, with a small bore, passing 

 through, and within an eighth of an inch of the bottom of, the former, its 

 upper end being open to the atmosphere, but communication with the latter 



and the interior of the tube d, is prevented by making its passage through 

 the piece c, air-tight ; /, is a pipe, of about half an inch bore, passing through 

 the ship's bottom, as near midships as convenient ; g, is a mouth piece or 

 cover, having an aperture parallel with the keel; A, is another pipe similar 

 to the first, but without the mouth-piece g, (or the two pipes may be made 



in one, like a double barrel gun, in the passage through the ship's bottom) . 



i, is an elastic tube of vulcauised india-rubber, completing the connexion of 

 the apparatus. 



The instrument being understood, its action will readily be perceived. As 

 the mouth-piece J, is turned in a direction with the vessel's moliou it is evi- 

 dent that an upward pressure in the tube /, will take place in proportion to 

 the velocity of the vessel ; and as this upward pressure will be exerted on the 

 top of the mercury, it follows that the latter will rise in the small tube ex. 

 actly in the same proportion, and will indicate, by means of a gradual scale 

 the number of miles and any fractional parts thereof into which the scale 

 may be divided. In fixing the apparatus, care must be taken to keep the 

 bulb of the tube d, a few inches below the light-draft water-line. Now 

 when the vessel is deeply immersed, the column of mercury will rise in the 

 small tube to counteract the pressure of the water (about four-fifths of an 

 inch for each foot of immersion), consequently the scale must be made to 

 slide on the tube d ; the pipe h, and cock I, are for the purpose of adjusting 

 the scale with the depth of immersion, and is effected thus : — shut the couk 

 k, and open the cock I, and the mercury will adjust itself to balance the 



