18J6.] 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



39 



really do not see why a mass of matter, in the form of a cjlin Jer, slioiild be 

 more formidable or intractable in its movements than a similar quantity of 

 matter in the form of a side lever, or in any other sliai)e whatever. 



" It has also been objected against the oscillating engine, that the 

 eduction passages are more tortuous ihan in coninion en;;iues, so that the 

 steam gets out of the cjlinder less freely. We do nut believe such lo be 

 the fact, if the comparison be made with the ronimnn run of marine engines; 

 and in practice, no diminution of elMcacy from this cause is appreciable. 

 The fact is, all the objections ibat have been raised lo the oscillating engine 

 are merely hypothetical; they are anticipations of defects to be found out 

 in large engines on the oscillating plan, and would probably be plausible 

 enough to carry some weight, were it not the fact, that they have been 

 completely controverted by experience. The remark, indeed, is heard 

 Bometimes even yet, that the oscillating method may do very well for small 

 engines, but is of doubtful efficacy for large ones. But the definition of 

 large en"ines has been continually changed, to escape the contradiction ex- 

 perience afl'orded, and that size is, in every case, decided to be large, 

 which just exceeds the size of the oscillating engine last constructed. It is 

 plain, however, that the grounds of tnis scepticism are being fast contracted; 

 and, indeed, we think it requires a little cojitroversial intrepidity to set 

 down engines of C2-iuch cylinders, which is the size of those of the '• Black 

 Eagle," as among the number of small engines. And if engines of this 

 size are found to operate well — and those of the '• Black Eagle" have been 

 found to perform most satisfactorily — it really appears to us impossible to 

 suppose that engines of 5 or 10 inches more cylinder would not be found 

 correspondingly effective." 



The points here discussed are many of them of that complicated nature, 

 that independent reasoning will not suflice for the decision of them. The 

 ultimate verdict must depend on a much more extended experience ihan we 

 at present possess. However, notices such as the above, in which engines 

 of each kind are examined together and their defects compared, have the 

 happiest elfect in removing prejudices. 



Weale's QuarterVj papers on Engineerhi!;. Part IX, quarto, p. p. 240. 

 23 engravings, Weale, High Holboru. 



The present Part of Jlr. Weale's series of magnilicently printed and 

 illustrated volumes, is that for Michaelmas 1845, but the publication of it 

 has been unavoidably postponed to January 1846, owing, as it is stated, 

 to " the engagements in Railway matters of two of tlie gentlemen contri- 

 butors." There are four papers in the present number ; of which the first 

 and third may be considered together, as both are chiefly of a historical 

 nature ; the subjects of them being respectively " iheProgressof Machmery 

 and Manufactures in Great Britain, from the earliest times to Queen 

 Elizabeth," and "a memoir of the Thames Tunnel. Section II., by 

 Henry Law." The first of these papers gives a historical account of the 

 progress of the arts, year by year, in England ; the principal enactments 

 affecting manufactures and inventions, the importation of foreign improve- 

 ments, &;c. Some of the notices are very curious and interesting. — In 1404 

 ■we fiud Henry IV. ordaining " that none henceforth shall use to multiply 

 gold or silver, nor use the craft of muliiplication under the pain of felony." 

 The paper closes with an account of the disputes between Elizabeth and 

 her Parliament, respecting the royal, fondly -cherished, privilege of granting 

 patents for monopolies. 



Mr. Lasv's paper is also interesting, and will be very acceptable to those 

 who feel the value of tracing the /tjsfory of Engineering. This branch of 

 knowledge is much neglected at the present day; we seem content with 

 ascertaining the actual state of Engineering, and care but little to know 

 how and by whom the advancement of practical science has been effected. 

 The paper on the Thames Tunnel supplies a very important point in the 

 annals of mechanics. It details in distinct and forcible language the 

 wonderful skill and patience by which the difficulties attending that great 

 work were overcome, and deserves to be read with the greatest attention. 



The second paper is entitled " Praclical and Experimental Researches in 

 Ilijdraulics, by R. H. Peacocke, E. C. ;" the object proposed is to suggest 

 formula; for calculating the discharge of water from pipes, inc. The first 

 investigation which the author makes, tends to show that the curve which 

 water assumes when discharged from a pipe is not a parabola. It m ly be 

 as well to remark, in limine, that the form of the curie in which water 

 actually falls is never taken to be exactly a parabola; because it is 

 natural to conclude that if a projectile in air do not describe a parabola 

 neither will falling water. Mr. Peacocke, suggests a formula for calcu- 

 lating the curve of falling water in the following terms ; 



" The hydraulic curve consists of ordinates of a parabola plus, (some- 

 times minus) a certain constant quantity which increases arithmetically 

 as the corresponding abscissse increase." p. 3. 



.. It is not very easy to see how a ''certain constant quantity" can increase 

 arithmetically ; and we find out afterwards that this quantity is no /«c(o?- 



at all, but something to be simply added to, not multiplied by, the length 

 of the ordinate. He apprehend Mr. Peacocke's meaning to be— that his 

 curve is found by adding to, or substracting from, the ordinates of a 

 parabola, quantities proportional lo the corresponding abscissa;. For 

 instance, in his first experiment he substracts from each ordinate the decimal 

 part .07 of each corresponding abscissa, in the second experiment he 

 substracts '09 of each abscissa;, itc. Butone great defect which seems 

 fatal to his formula is, that it leaves quite undetermined ivhat proportions 

 of the abscissa; are to be substracted. These decimal parts .07, .09, &c., 

 are wholly empirical, and only suitable for the particular cases to which 

 they are respectively applied. He, himself says, of his " factors," as they 

 are termed throughout, 



'• In Experiment 1. The factor is — .07. 

 „ 2. Ditto -.09 



„ 3. Ditto —. a minute quantity not ascertained 



„ 4. Ditio -f.03 



„ 5. Ditto 



On comparison of these factors, and consideration of them with reference 

 to the lengths and diameters of the tubes, and the amounts of " head" — it 

 is not observable that the factors follow anij definite law ; though it is 

 probable that a greater number of experiments would have proved the ex- 

 istence of a definite law. But the farther prosecution of the subject in 

 that way, though it would have been interesting, was not necessary to my 

 present purpose." 



So that we really cannot see in what way we are the wiser for his ex- 

 periments. In two out of five of them he does not determine any " factor" 

 whatever, and in the remaining three the factors apply only to the particular 

 cases and suggest no general law. 



It is important to remark that Mr. Peacocke merely observed the form 

 of the curve near the orifice. His experiments for the determination of 

 the curve do not extend to a fall of four feet below the discharge pipe. 

 Now it is very possible the proposed formuhe may represent a curve, re- 

 sembling that of falling water near its source, but widely diverging from it 

 at a great distance from the source ; for with short lengths of the curve, 

 errors would not be easily detected. It may readily be conceived that by 

 Mr. Peacocke's system of " factors" (determined, it is to be observed, 

 separately for each case,) he may get a formulae which coincides with the 

 results of his experiments as far as they extend, but not much farther ; — 

 and we must be excused for adding that it is also possible to conceive the 

 existence of a formula of entirely different shape, and involving altogether 

 diflereut functions, which would represent the form of the curve both near 

 and at a distance from the origin. 



The experiments are followed by an examination of formula, proposed 

 by Mr. Smeaton, M. Prouy, Dr. Young. Chevalier Dubuat, M. Eytelwein, 

 &c. for the discharge of water. The following conclusions are ultimately 

 made. 



"Isf. How nearly the experiments are a mean of the two extreme formulae, 

 namely, those of 51. Eytelwein and M. Genieys. 



2ud. How nearly the experiments are a mean of the two next formulae, 

 namely, those of Sir. Smeaton and Chevalier Dubuat. 



3rd. How very nearly the experiments are a mean of the two most ac- 

 curate formulae, namely, those of M. Prony and Dr. Young. 



I think no scientific man will,after satisfying himself that my calculations 

 are correctly made from M. Eytelwein's and M. Genieys' directions, make 

 use of either of these gentlemen's formula;." 



Having some curiosity to know on what data the condemnation of 

 Eytelwein's formula;, which has considerable reputation, was founded, we 

 turned to Mr. Peacocke's examination of that particular formnlfe, and 

 found that he had by his own showing, taken the value of one symbol at 

 ouefourth of that intended by Eytelwein. He says that Dr. Young 

 understands the symbol d in the formula; " to signify the diameter, (of the 

 discharge pipe) while I understand it to mean the hydraulic mean depth, 

 or one-fourth of the diameter of the pipe," and then adds in a note that he 

 finds on reference to the original work in German, thatDr. \oung is ■ 

 right, but that he himself was misled by the Encyclopiedia Britannica. 



" I have, since this essay was in type, referred.to M. Eytelwein's original 

 work in German ; and have found that rfsigciiSes the diameter, consequently 

 the writer in the Encyclopa;dia Britannica has (unintentionally of course) 

 mis-stated M. Eytelwein's formula." 



The paper certainly evinces great labour, but such an error as the above 

 is rather a serious one; and the writer must nut be surprised to find that 

 in a subject which has baflled the sagacity of the acutest philosophers, the 

 proposition of new empirical formula will be regarded with distrust, unless 

 they be supported by a weight of testimony far exceeding any hitherto 

 collected. 



The last paper is a report of the Institute of France, on M. Arnolett's 

 system of Atmospheric Railway. This paper is translated and prepared 



