1848.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



211 



only one particular case — that of circular motion — in which the 

 above definition is satisfied. In elliptical and other kinds of motion 

 it is violated at every instant. This consideration is of itself 

 sufficient to show that the third definition is also incorrect. Cen- 

 tral forces are always taken by mathematicians to be forces directed 

 from or towards a fixed centre — which centrifugal force is not. 



The laws of motion about centres of att ration are applied to 

 cases to wliich they have no relation. The following problem is an 

 instance : — 



" If a fly, 2 tons weight and 16 feet diameter, is sufficient to regulate an 

 engine when it revolves in 4 seconds; what roust be the weight of another 

 fly of 12 feet diameter revolving in 2 seconds, so that it may have the same 

 power upon the engine ?" 



It seems scai-cely credible that the solution of this problem is 

 derived from the law of motion of a free body in a circle about a 

 central force — that " the forces are as the distances or radii of the 

 circles directly, and the forces inversely." Could it be believed, 

 that a student viho had read mathematics for six months, would 

 apply a law, which is wholly independent of tlie mass acted upon, 

 to a problem in which the mass is the most essential particular .'' 

 By such log-ic, the following relation between the weights of the 

 two fly wheels is established : — 



WD _ wd 

 T' ~ P ' 

 where W, «>, are the weights; D, d, the diameters of the wheels; 

 and T, t, the times occupied in revolution. Now, to show the ab- 

 surdity of all this, we have only to express the times in terms of 

 the linear velocities, V, and v, and the above equation becomes 

 W V= _ wv\ 

 D ~ d ' 

 which leads to the conclusion, that for two fly wheels of equal 

 weight, that having the greatest velocity must also have the greatest 

 diameter ! — a conclusion to which our practical readers would pro- 

 bably demur. 



It would take up too much space to e3£j)lain all that appears 

 objectionable in the work before us. Mr. Law certainly has the 

 credit of rendering the new edition somewhat better than the pre- 

 ceding, by introducing De Pambour's investigations of the power of 

 the steam-engine, and by several improvements of arrangement. 



In the pajier on the Strength of Materials, which is almost en- 

 tirely re-written, Mr. Law gives some valuable views of the subject, 

 which cause us to regret that he has not exercised keener criticism 

 in other parts of the work. In estimating the tranverse strength 

 of materials, an ingenious theory is proposed, for representing the 

 total forces of extension and compression in any section of a girder 

 by solids, of which lines proportional to those forces are the hori- 

 zontal ordinates. Unfortunately, he overlooks the fact that the 

 total forces of longitudinal compression and tension are equal and 

 opposite. He assumes also that their moments are equal — which 

 is incorrect. This error vitiates equation (I), page 373, and all 

 that depends on it. 



Our review must close here, not from want of subjects for further 

 comment, but because of the space which they would occupy. We 

 have done little more than point out, in the briefest possible man- 

 ner, a few errors here and there; and have avoided general observa- 

 tions, lest our criticism should appear unduly severe. 



The High-Pressure Steam-Engine ; an exposition of its Comparative 

 Merits, and an essay towards an Improved Si/stem of Construction. By 

 Dr. Eknst Alban, practical machine maker, Plan, Mecklenberg. 

 Translated from the German, with notes, by Wiujam Pole, C.E. 

 London: Weale, 1848. 8vo. pp. 150. 



This is the conclusion of a work of which the first portion was 

 reviewed ante, vol. X., p. 45. It will be remembered, that the 

 distinguishing feature of Dr. Alban's subject is an earnest advo- 

 cacy of the merits of the high-pressure steam-engine, which, he 

 contends, is for all purposes and under all circumstances, superior 

 to the low-pressure engine. He proposes to increase the steam- 

 pressure greatly beyond the limits now usually assigned to it ; and 

 as his observations are the result of long practical experience in 

 the manufacture of engines, and in superintending their working, 

 they are at least deserving of consideration. His arguments are 

 those of a careful and judicious observer, and the details of his 

 experience prove that he has pursued his profession with no ordi- 

 nary amount of energy and ability. 



In the present portion of the treatise, our author describes the 

 form of the boiler and furnace adopted by himself, and which he 

 recommends as models for general adoption. We must demur, how- 



ever, to the notion of a model engine, and to any one routine of con- 

 struction prescribed for universal practice. The steam-engine 

 would lose much of its value if the arrangement of its parts were 

 immutable. The diversity of forms which may be given to it, 

 and the facility of adapting them to local exigences, render the 

 steam-engine the most convenient, as it is the most economical, 

 of motive agents. c d 



The principle which characterises Dr. Alban's o o o 



boiler, is the circulation of hot water through o o o o 

 the tubes, and the return to the boiler of the o o o 



water which has been carried upwards in a liquid o o o o 

 form with the current of steam. The dots in the o o o 



diagram will sufficiently explain the relative o o o o 

 position of the tubes, c, d, are two capacious vessels above them. 

 The ends of all of them communicate with c, the "separator," 

 into which, therefore, the steam generated, and the water mechani- 

 cally mixed with it, are carried. At that end of this vessel 

 where steam and water are admitted, violent ebullition goes on ; 

 but as the capacity of the boiler is large, the water and steam be- 

 come more and more separated as they progress to the further end, 

 whence they pass quietly by their respective pipes to tlie receiver 

 d, in which an undisturbed water-level is maintained. From d, 

 the steam passes oif to the engine, and the water is returned to 

 renew its labyrinthine course through the tubes of tlie boiler. 



Our author assures us that he has determined the efficiency and 

 economy of this invention, by actual and careful experience. The 

 advantage which he claims is, chiefly, that of having a tube 

 surface, subject to the direct action of the furnace, aud yet not 

 liable to excessive ebullition or boiling dry. The tubes are of 

 small diameter ; consequently, their heating surface bears a liigher 

 proportion to the volume of water in them, than would be the 

 case with tubes of a larger diameter. This circumstance. Dr. 

 Alban insists upon as most important for the economical generation 

 of steam. At the same time, the tubes lie so far below the water' 

 level, that a want of water in them is scarcely likely to occur : 

 and if it did, it would take place first in the higher tubes, which 

 are the least exposed to heat. 



It will strike some of our practical readers, that this mode of 

 construction, and the smallness of the tubes, must render them 

 exceedingly liable to be impaired by the accumulation of deposit. 

 We are told, however, that this is by no means so formidable a 

 difficulty as it may at first sight appear, as the stony concretion 

 is confined to the upper tiers of tubes, and the arrangement 

 aifords easy access to them. It is however allowed, that tubes of 

 so small size as those here described would not be applicable to 

 marine boilers, in which a great deposit from salt water takes 

 place. 



After a minute description of the boiler, the writer proceeds to 

 an examination of improvements of the furnace. He does not 

 deem of much importance the " smoke nuisance," as it is em- 

 phatically termed in England, and decries the legal restrictions to 

 which engine owners are subjected in Germany, to prevent them 

 from forcing the bituminous vapour and soot of their furnaces 

 down their neighbours' throats. " The English," says he, " con- 

 tinue to live well among their smoke, and find themselves well off 

 on it ; they neither turn up their noses nor get asthma, but they 

 live, and live long." We, however, who live in England, are not 

 easily to be persuaded that the vitiation of the air by smoke is a 

 slight evil. The pollution of the air in London and the manufac- 

 turing districts, inflicts mischief of which tlie magnitude can only 

 be appreciated by actual observation. The cities of the continent, 

 by the limits of their size, and the comparative insignificance of 

 the manufactures carried on in them, are so little subjected to the 

 injury in question, that it is not surprising that a foreign writer 

 should speak slightingly of it. But the thousands who annually 

 fall victims to the chimiiey-poUuted atmosphere of this metropolis, 

 give mournful proof that it is no false sentimentality — no popular 

 prejudice, that have at length rendered the sanitary regulation 

 of manufactures an irresistible obligation on the legislature. Dr. 

 Alban considers all the self-acting contrivances for consumption 

 of smoke useless ; and deems it vain to expect that any future 

 inventions for the purpose will succeed. It is sincerely to be 

 hoped, however, that an object of such paramount importance will 

 not be given up in despair. There can be no question that much 

 improvement has already been effected, and that the combustion 

 of fuel is conducted in a more complete and perfect manner now 

 than it was a few years ago. When the necessity of further exer- 

 tions becomes apparent, that parent of invention will stimulate 

 our mechanicians to greater efforts and to the discovery of 

 methods which, we are convinced, have not yet been attained, 

 because the inquiry has been partially or feebly conducted. 



28* 



