1842.1 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



119 



hi 



ii "A most materi.il circumstance aftecting the utility and economy of 



H steam vessels of great power, is the space necessarily occupied by the 

 P engines and the supply of coals, which are found to require three- 

 fourths of the whole area below deck, leaving only one quiirter for the 

 stowage of cargo : and that, owing to the great weight of the former, 

 must principally consist of measurement goods. Thus the " President" 

 and the "British Queen," although of 2000 tons register, have never 

 been able to carry more than 500 tons of measurement goods asi'reiglit. 

 " From a due consideration of these features of the question, with 

 respect to the expediency of employing large steam vessels (and it is 

 believed that few practical men will dispute the facts by which they 

 are developed ), it is evident that the attempt to perform voyages of 

 lengthened duration by the power of steam alone must, in the present 

 state of engineering science, be attended with an expense wholly 

 disproportionate to the profits." 



"The present state, therefore, of steam navigation is evidently 

 altogether inadequate to meet the large and daily increasing demands 

 of commerce ; and in this respect, as far as maritime navigation (as 

 contra-distinguished from river and coast navigation,) is concerned, 

 steam must be considered to be in its infancy, ifor the communication 

 by this means with our own or with foreign distant colonies — India, 

 via the Cape of Good Hope — the West Indies — the Paciiic Ocean — 

 Australia — the Brazils, and other highly productive countries, is at 

 present impracticable to any extent, as the facts hereafter stated will 

 more distinctly show." 



"Before entering upon the details of this scheme, either as regards 

 its past success in the partial and limited application which it has 

 hitherto received, or as to its future adaptation, it may be desirable to 

 describe the class of sailing; vessels to which auxiliary steam may be 

 regarded as an applicable power, and where its employment may be 

 expected to be attended with success; and here it must be observed, 

 that commercial and not scientific success is the result looked to, for 

 nothing can be considered successful in a commercial point of view, 

 to which a fair profit upon the capital employed does not attach." 



The definition of the term "success" here given might be looked 

 upon as unnecessary, had we not before us the remembrance of the 

 strange perversion of the plainest language, during the discussion of 

 the Atlantic steam enterprise. In that case success was regarded as 

 synonymous vi;ith practicability. 



Mr. Seaward informs us that auxiliary steam power is beneficially 

 applicable to all vessels, from 400 tons upwards, and that the propor- 

 tion of one horse power to 25 tons will propel a vessel in a calm at the 

 rate of 5 knots per hour. He then institutes a comparison between 

 the time occupied by the ship "Vernon," fitted with auxiliary steam 

 power, on her voyage from London to Calcutta, and that of the steam 

 ship "India," which performed the same voyage about the same 

 period. The expenses attendant upon the employment of auxiliary 

 steam power in the "Vernon" during this voyage are stated to have 

 been£G00; whilst the expenses attendant upon the "India" for the 

 same period are estimated at £4293, showing an excess of expen- 

 diture over that of the " Vernon" of £3(393. The comparative rate 

 of the vessels in point of speed, as stated by Mr. Seaward, appears by 

 DO means favourable to the " India ;" but, as we know the " India" to 

 have been detained for a considerable period at the Cape by stress of 

 weather, and as we conceive there are evidences of some slight pre- 

 judice against the "India," in consequence, we presume, of her being 

 a Clyde-built vessel, we attach but little value to this part of the 

 statement. 



Mr. Seaward's memoir contains much important information, and 

 manifests a familiar acquaintance with the subject of which he under- 

 takes to speak, and the possession of a liberal share of good common 

 sense. It is also well written, though we should have been better 

 pleased with it had there been less straining after rhetorical decora- 

 tion ; a serious fault in any pai)er which professes to treat of practical 

 and scientific subjects, especially when addressed, not to the herd of 

 mechanical amateurs, or scientific cyphers, but to an association of 

 able and practical men. Another fault which pervades the work, is 

 the frequency of reference to, and of involved commendation of, the 

 Messrs. Seawards' engineering performances. We hear a great deal 

 too much of the excellencies of tlie "Gem" and the "Ruby," and we 

 find those vessels and the " Brunswick," the latter a work also of 

 Messrs. Seaward's and a comparative failure, associated with and 

 obtaining the precedency over the "Eclipse," the "Black wall," and 

 the "Railway," vessels by which, in point of speed, they are entirely 

 outstripped. Such preferences as these inanifest an unbecoming 

 partiality, as ill-judged as it is impotent; and are equally unworthy 

 of those' by whom such communications are accredited as of those by 

 whom they are rendered. 



In conclusion, Jir. Seaward observes that he has avoided all recon- 

 dite calculations, with a view of meeting more effectually the objects 



of practical men. He further informs us, that theoretical calculations 

 upon such a subject as that he has undertaken to handle, however 

 suited to the jihilosopher's study, are of little value to the practical 

 engineer or ship builder ; and he quotes the language of the late Pre- 

 sident of the Institution of Civil Engineers, to the effect that, what is 

 wanted for that society is the development of that knowledge 

 which is founded upon practical experience. From this intimation 

 we might infer that, in the opinion of this gentleman, science is 

 incapable of rendermg any aid to the practical mechanist, but that 

 he vsiould be prepared to go into the most recondite computa- 

 tions, were such a couise desirable. In reference to the first allegation, 

 it is only necessary to observe that, in the development of that know- 

 ledge which is founded upon practical experience, science is the most 

 efficient instrument ; in proof of which fact, we might refer to the 

 extraordinary development the arts have experienced since their 

 progress has been aided by the light of science, as compared with 

 their stationary condition when they were merely empirical. As 

 regards the second implied allegation, namely, th.it Mr. Seaward would 

 be prepared to enter into extremely recondite calculations respecting 

 the subject of his memoir, oxceptfor the weightv reason he hasgiven, 

 we can only admire the discretion which dictated so much forbearance. 

 If it be Mr. Seaward's desire to maintain his reputation for profundity, 

 he will best accomplish his object by avoiding all attempted manifes- 

 tation of it. The only attempt of this description in the memoir before 

 us is in the 4th page, where we are told that " the employment of a 

 quadruple amount of steam power would not double the speed, al- 

 though in theory this is assumed to be the fact." By whose theory is 

 this assumption made ? We presume that it must be of Mr. Seaward's 

 own fabrication, and his exclusive property, it being the theory of 

 other engineers that the resistance increases as the square of the 

 velocity, and the power necessary to overcome that resistance, as the 

 cube of the velocity. And the reason is obvious. If the power be 

 doubled, the resistance is quadrupled ; the force of the engine, there- 

 fore, to overcome this resistance, must be quadrupled also, and must 

 act with a double speed. In other words, when the speed is doubled, 

 the power requisite to maintain that speed has to be increased eight 

 times instead of four times, as by the Ihorij of Mr. Seaward. 



A Treatise on the Application of Marine Surveying and Hydrometty 

 to the practice of Civil Engineering. Bv DA'ao Stevenson, Civil 

 Engineer. Adam and Charles Black, Edinburgh, 1S42. 



The author here treats on a branch of surveying which has always 

 been very imperfectly handled in works professing to convey infor- 

 mation on this subject. The quaint and pithy directions of old writers, 

 when they come to show the manner of surveying the coasts of har- 

 bours and rivers, will seldom fail to elicit a smile from the professional 

 surveyor, at the idea that such directions would ever enable any one 

 to perform what they are intended to teach ; and scarcely less will 

 he be moved by a mingled feeling of pity and ridicule for any unfor- 

 tunate would-be surveyor, who, deeply read in the mystic lore of some 

 ancient authority, should sally forth, in all confidence, to the task of 

 performing a difficult river or harbour survey. Were it not that the 

 practice and the knowledge of surveying are confined to a compara- 

 tively small number of persons, and that, consequently, errors which 

 are made in surveys, and bungling, roundabout ways of proceeding 

 are not often observed, we should undoubtedly have evidence enough 

 to prove the necessity of practical information on a subject of such 

 importance. If we could lay bare the secret trembling anxieties, the 

 harassing emotions, the suppressed fears and doubts on the ultimate 

 success and accuracy of his work, which torture the young surveyor 

 in his hours of arduous application, whether in the field, poring 

 over his theodolite and the hieroglyphics of his field-book, or in the 

 house, straining over the net-work of his survey, as by slow degrees 

 he develops it on the paper, we should even feel that a boon is con- 

 ferred on humanity by a [iroduction which reduces to order and 

 simplicity the details of a task calculated to puzzle, in no small degree, 

 the ardent hasty brain of a youthful student. We therefore hail the 

 book before us, judging froiu its title alone, and supposing it to have 

 any merit at all, as a welcome accession to the engineer's library ; our 

 expectations also, on a first glance, were not diminished when we 

 recognized its author to be the same Mr. Stevenson who favoured the 

 profession not long since with an instructive work on the Civil Engi- 

 neering of North America. Mr. Stevenson also boasts of a name not 

 less celebrated in Scotland than that of his namesake in England, the 



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