344 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



rOcTOBKR, 



neglectetl, that ii^, from tlie nitiment when the eduction port is opened 

 to tlic termiii;ition of tlie stroke : for, on account of the very small 

 opening of the ])ort during tlint period, very little steam is enabled to 

 escape, and it had previously been but slightly reduced in pressure by 

 expansion, so that its mean pressure during this last portion of the 

 stroke will bear a considerable proportion to its initial |)ressure, and 

 cannot therefore be neglected. On the other hand, the elTect of the 

 compression of the spent steam of the pressure /, between the instant 

 of shutting the eduction valve and that of opening the steam valve, is 

 so small that it might much rather be disregarded ; for it commences 

 with a pressure of about 1 atmosphere and terminates with about 1-4, 

 say on an average .1 atmosphere through one-fortieth part of the stroke, 

 or about one-tenth of a th. through the stroke, due to compression. 



Thirdly, Mr. Lavvrie makes the inexplicable assumption that the 

 safetvvalve be so loaded that /)::= s — the initial pressure of the steam 

 in atmospheres^ the area of the piston I — Supposing the square foot 

 to be the unit of area, and s= 1 square foot; we should then have 

 p= 1 atmosphere, and the engine would not move; but if the square 

 inch were the unit of area, for the piston of the same size as before 

 we should have s=: Ml square inches, and consequently ;^ = 144 at- 

 mospheres !=rT!iese results show the manifest absurdity of the sup- 

 position. 



Lastlv, the values of a', b and c', in the examples which close the 

 paper, are not determined correctly from the formula; which, I said 

 above, are themselves correct, so that the whole paper requires revi- 

 sion and correction, except the first part, as I have explained. 



Hoping that the above remarks may be found serviceable to your 

 readers, 



I remain, &c., 



M. 



MR. JOSIAH PARKES IK REPLY TO COUNT DE PAMBOUR 



Mr. Editor — M. de Pambour has recently repeated, in several of 

 tlie weekly and other periodicals, certain virulent strictures on my 

 writings. I am at a loss to conjecture on what grounds that indivi- 

 dual should have indulged in these, as well as in his earlier, and nearly 

 similar, attacks upon me. I have, hitherto, declined replying to them, 

 and for two reasons ; first, I did not wish to convict a man of M. de 

 Pambour's celebiity of deliberate misrepresentation; nor, seeondiv, to 

 expose, more publicly than he had himself done to persons really con- 

 versant with the steam engine, his lamentable ignorance of practical 

 matters. But, his resumption of these attacks, in the present form, 

 renders it incumbent on me to be no longer silent. I, therefore, avail 

 myself of the same medium of communication, and shall confine my 

 reply to the exhibition of one instance of his gross ignorance, and of 

 one instance of his numerous, and injurious, falsifications of my o])inions 

 and writings. 



Every engineer is acquainted with the cataract, an instrument nearly 

 as old as Newcomen's engine, and used for the purpose of opening the 

 steam induction valve, and thus starting an engine, after any required 

 period of rest. This s])ecies of water clock is also occasionally em- 

 ployed to open other of the valves at definite times. The Cornish 

 engineers a])preciate its value, not only as a means of regulating the 

 number of strokes to be made by a pumping engine, in a given time, 

 but also as efl'ecting the influx of steam into the cylinder in the most 

 instantaneous manner. Neither they, nor any other engineer ever, 

 probably, imagined the cataract to exercise an influence over the pro- 

 duction (ifstiam in the boilers of their engines. The Comte de Pam- 

 bour, however, ascribes to the instrument this miraculous virtue, in the 

 following passage : 



"We will finally remark that it is customary in these engines to 

 make use of the cataract. Under this circumstance the engine docs 

 not evaporate the full quantity of water, that its boiler would other- 

 wise be capable of evaporating per minute; but, on introducing into 

 the formulffi the evaporation really eftected, the formula; will always 

 give the corresponding effects of the engine." — (New Theorij of the 

 Steam Engine. J. Weak, 1839, chap, xi., Cornish Si/igle Pumping 

 Engine, p. 278. J 



This !s, verily a neiv theory. No observations of mine are requisite 

 to illustrate the absurdity of theories, and formulae, emanating 

 from a person who is so little practically versed in the mechanism, 

 and auxiliary apparatus of an engine, as to jumble together, and con- 

 found, in one paragraph, the distinct functions of the cataract, the 

 boiler, and the engine. 



[n a later work, M. de Pambour has devoted no less than IG pages 

 of introductory matter to a criticism of my Paper on the Locomotive 

 Engine, (published in the Transactions of the Institutution of Civil 

 Engineers, vol. iii.), in which, among others, I had occasion to examine 



his own experiments. In that paper not a word will be found dis- 

 respectful of M. de Pambour ; his sentiments are treated with cour- 

 tesy ; and, at the ri^k of being thought tedious, I prefaced each of my 

 observations on his conclusions with a quotation of the matter com- 

 mented upon. M. lie Pambour's reply contains numerous misappre- 

 hensions of my meaning, and arguments, of which I do not complain; 

 but every author has fair ground of complaint against the antagonist 

 who perverts his text ; who invents arguments for him; or who cites, 

 as authentic quotations, phrases which he never employed. In no one 

 instance has M. de Pambour quoted mv own words; in lieu of which 

 he has frequently«invented words and opinions for me. The following 

 extract affords a concise example of the veracity and style of the IG 

 pages of criticism. 



"The want of using equations which facilitate so much accuracy in 

 mathematical reasoning (iih(/ Mt author accountufor it in telling un thai 

 he is more accustomed to handle his hammer than his pen,) causes him to 

 heap errors on errors, combining and complicating them unaware, till 

 he arrives at a point where he does not produce a single result that is 

 not erroneous." — (.-i Practical Treatise on Locomotive Engines, 'IniX 

 edition. J. Weale, 1840. Introduction, page xxxiii.) 



The paragraph in italics is a pure invention. No such v ords even 

 occur in my paper as hammer ov pen. 



The writer who resorts to the miserable tactics of falsifying the 

 language and opinions of one who differs from him on subjects open to 

 large controversy, exhibits a consciousness of inferiority in his argu- 

 ments, which it would have been wiser, and far more manly to ac- 

 knowledge, than to attempt to conceal, by expedients so unworthy, 

 and so certain of detection. Such a man may, possibly, be a skilful 

 mathematician, but he cannot claim rank among philosophers, whose 

 sole objects are the discovery and propagation of /;-«M. I consider 

 myself exonerated from all obligation to reply, in greater detail, to an 

 adversary who descends to such ignoble practices; but justice to my 

 own reputation requires that I should expose them to public reproba- 

 tion. This I do with the more regret as I have derived both instruc- 

 tion and pleasure from some parts of M. de Pambour's researches. 

 I remain. Sir, your obedient servant, 



J05IAH Parkes. 



12, Great College-street, Westminster, 

 September 13, 1841. 



LONG AND SHORT CONNECTING RODS. 



Sir — In your September number there are two communications an- 

 imadverting on my paper on connecting rods in the July number. In 

 this paper, my object was to establish the soundness of the connecting 

 rod, m general, as a medium of moving force, and thereby to endea- 

 vour the settling of the controversy about long and short rods. For 

 it is not disputed by any, I presume, that the strains and consequent 

 friction between moving parts, in machinery, occasioned by connecting 

 rods on the same crank, are in a certain proportion to their lengths ; 

 and I agree that herein longer rods have the advantage of shorter. 

 But the question has been, whether, purely as transmitters of force, 

 the former has any superiority to the latter, which leads to the ques- 

 tion whether generally and abstractly, connecting rod motion is just as 

 a medium of force. As I have said, it was my object to prove the 

 affirmative of the question. Therefore, in this view of the subject 

 rods of difl'erent lengths to the same crank ought to be one in effect. 



Though certainlv I did not notice the fact, 1 was aware that the con- 

 necting rod would not work on a crank of the same length in the usual 

 style. We may mention, however, that a modification of this case is 

 in fact practised in epicycloidal motion, a demonstration of which is 

 given in March number for last year, in which the stroke of the piston 

 is twice the throw of the crank, and the radius of the inner wheel is 

 the connecting rod. 



I am, Sir, your's, obediently, 



D. Clark. 



Glasgow, September 16, 1S41. 



Artesian Well at Gmiclti-.—V. Malot, in some of his recent exiirrimciUs at 

 the Artesian well in the abattoir of Gr.nellc, succeeded in furcin^' the jet of 

 water as hi{;b as 63 feet above the ground, and when it reached this heiyht, 

 the water assumed a bell shr.iie, ten metres in diameter, which produced the 

 most picturesque eflect. Untortunalcly the water continues muddy ; there- 

 Cure, thiaigli there is a certamty ot being able to procure nearly 2000 litres 

 of \ialer in the course of a minute, at a height wliich admits uf its being 

 conveyed into the highest stories of the houses in Paris, it is not yet known 

 to what purposes the water can possibly le applied. 



