384 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



[November 



ILe pressure in the boiler were precisely the same, and the regulator opciicil 

 to the same degree in the second as in the first experiment, equal power 

 juust have been generated and expended in the same time, though at the 

 liighcr velocity, the lighter load was moved through a greater space in that 

 lime. Had >i. de Pamboiir reduced his data to the terms of value in these 

 tables, he must inevitably have discovered the numerous errors of fact, and 

 deduction, which are now brought to light." 



So, it is clear that we did not misrepresent the sentiments of Mr. Parkes 

 T^hcn, in our former paper, we said that he concluded against the accuracy of 

 the experiments, because in the two cases cited, the useful cfTccts of the en- 

 gine bad not been the same. But we liave ])rovcd, in that paper, that in 

 Kpitc of an equality of pressure in the boiler and of opening of the regulator, 

 there is always more loss supported by the engine, in overcoming its friction, 

 the resistance of the air, &e., at a great than at a small velocity. Therefore, 

 the useful eficct produced, or effective horse power ought not to be similar in 

 the two cases ; and the " numerous errors of fact, and deduction, which are 

 now brought to light," by the Crilic and his fables, are nothing but a new 

 misconception. 



5th. Ve have said that Mr. Parkes submits the two same experiments, and 

 the other experiments afterwards, to the test of a new princijile, which con- 

 sists merely in his making a confusion between the vaporizations etfected in 

 traversing the same distance and the vaporizations effected during the same 

 time. This wUl be proved by the following passage, in which it will he seen 

 that Jlr. Parkes quotes our words relative to the vaporization /or the same 

 distance, and afterwards applies them to the vaporization in tlie same time. 

 Vie have marked in italics the words which make this misreasoning quite 

 evident. He says (page 99), " in bis Treatise on Locomotive Engines, (pages 

 310, 312), M. de Pamhour states a near parallel to these two experiments, by 

 supposing a case of the same engine, with the same pressure in the boiler, 

 travelling the same distance with two different loads. The distance travelled 

 Jjeing the same, the number of turns of the wheel, and consequently of strokes 

 cf the piston, or cylinders of steam expended will be the same in the two 

 cases. ... So the mass or weight of steam expended will be in each case in 

 the ratio of the pressure in the cylinder. . . . Kow the author has given us the 

 resistances on the piston which amount in the first case to 38-43 lb., and in 

 the second to 23-93 lb. per square inch ; and yet he assumes an equal ex- 

 penditure of water as steam, in equal times, in the two cases. ... To be con- 

 sistent, however, with his own rule, above quoted, viz. that the weight of 

 vater consumed as steam are to each other as the resistances on the piston, 

 it is obvious that if, in the first case, 3026 lb. of steam passed through the 

 cylinders in an hour, 21C61b. only would have been expended in the second 

 case." And (page 101), "But we have already seen that if the quantity of 

 vater were correctly taken in the first case, a less quantity must have been 

 consumed in the second, as the load upon the pistons of the engine in the 

 tv^'o experiments deduced from their velocity and assigned resistances, differed 

 in the ratio of 38-43 to 23-93 ; and the water as steam consumed, in equal 

 iimes, mtist necessarily have varied in the same ratio, or as 30261b. to 2166 

 lb. It would be fruitless to pursue this analysis further, and vain to attempt 

 the rectification of errors, — a task which properly belongs to the author." 



■\Ve see that the passage quoted from our work establishes distinctly that 

 vben an engine draws two different loads over the same ground, the quantity 

 ©f water vaporized, y&r the same distance, must be in proportion to the total 

 pressures of the steam in the cylinder. But Mr. Parkes concludes from it, 

 that the quantities of water vaporized, in the same time, must be in the ratio 

 of the pressures. But we have proved, in our former paper, that those two 

 consequences are precisely contrary to each other. Therefore the principle 

 alleged by >Ir. Parkes, and which he uses afterwards throughout bis paper, 

 to " test" the accuracy of the experiments, rests merely upon a new mistake 

 cf his own, which consists, as we have said, in making a confusion between 

 the vaporization /or t/te same distance, and the vaporization ybc the same time. 

 So that there is no occasion to "attempt the rectification of errors" dis- 

 covered by the application of this new principle. 



6th. Mr. Parkes comparing the locomotive with the fixed engines, says, 

 (page 90), " Thus the fixed non-condensing engine is the most economical of 

 the two ; but if Mr. de Pambour's data are correct, we must abandon all 

 preconceived opinions, and all belief in the accuracy of pre-ascertained results 

 on the non-condensing engine ; we must reverse our engineering creed, and 

 acknowledge the fixed non-condensing engine, with its simple atmospheric 

 resistance, to be far inferior, in economy of steam, to the locomotive, witli 

 its plus atmospheric resistance." And (page 98), " for it is utterly impossible 

 that the locomotive should accomplish an equal efl'eet, with i less steam than 

 the condensing engine. To go over this ground again would be a mere re- 

 petition of arguments previously used." 

 ' By these passages it is fiUly established that Mr. Parkes would, as we have 

 said in our former paper, conclude against the accuracy of the experiments, 

 because a locomotive engine cannot possibly produce a useful effect equal to 

 that of a high pressure non-condensing, or to that of a condensing engine. 

 But we have proved that the case may occur; and Mr. Parkes concedes it 

 himself (pages 156, 157), in saying of a sort of locomotive engine under his 

 charge, " the consumption of steam per effective horse power, per hour, has 

 been shown to be 1201b. for the fixed non-condensing engine, and for the 

 locomotive under review 112-54 lb., which proves the latter to have been the 

 most economical of the two, at nearly the same absolute pressures. This is 

 a new, and perhaps, an unexpected result." Therefore Mr. Parkes's first ob- 

 jection was good for nothing. But, besides, it must be borne in mind that 



the velocities used by Mr. Parkes, to calculate the effects of the locomotive 

 engines, being nearly all considerably increased, as has been proved above, be 

 must necessarily arrive at exaggerated results for the effects which he sup- 

 poses to have been produced by those engines. Therefore this new argument 

 against the accuracy of the experiments, is again the result of his own errors 

 of reasoning and calculations. 



/th. To prove that the same unfounded arguments have been urged by 

 Mr. Parkes, and with the same results, against every other engineer who has 

 published experiments on locomotive engines, we need only quote the follow- 

 ing passages. 



Respecting the experiments of Mr. Robert Stephenson, Mr. Parkes says 

 (page 105), "They contain within themselves abundant proofs of error in the 

 quantities assigned to the consumption of water as steam. ... >>'ow, if the 

 evaporative data are correct, it would appear by the ratio which the volume 

 of steam consumed bears to that of the water which produced it (^li^th being 

 deducted for waste), that the absolute pressure upon the pistons in this ease 

 amounted to 81-95 lb. per square inch ; but there was only 50 lb. in the boiler ! 

 If, therefore, 7" cubic feet of water passed through the cyUnders in an hour, 

 in the shape oi pure steam, the blast-pressure or counter-effort above the at- 

 mosphere, was 34-41 lb. instead of 2-{ lb. per square inch on the pistons." 

 And (page 106), "Experiment XII. In this case I have assumed an equal 

 evaporation in the same time as in the foregoing experiment -, and if ^ were 

 deducted for waste, the blast-pressure would be less than nothing — or a va- 

 cuum ; for, with the subtraction of } for waste, as in the table, the absolute 

 pressure amounts only to 11-lOlh., whilst the resistance required 101b. per 

 square inch ; and if, contrary to demonstration, it be considered possible that 

 the 77 cubic feet of water were converted into pure steam, and that this 

 quantity passed through the cylinders in the hour, the blast-pressure would 

 equal the whole force required to balance the assigned resistance ; for the 

 absolute pressure on the pistons woidd have amounted to20-70 lb. per square 

 inch, whilst the sum of ascertained resistance was only 101b." 



Respecting Dr. Lardner's experiments, Mr. Parkes says, (page 110), "It 

 appears, from the tenth conclusion, that the author considers his experiments, 

 so far as they have gone, as giving results in very near accordance. It can- 

 not fail to be remarked that the term discordance would seem to be much 

 more appropriate than accordance to the indications of the last column iu 

 the table. But no fair average can be struck from such irregular results ; 

 and (page 118), " If the resistance assigned by Dr. Laidner as opposed to the 

 motion of the train be correct, the efliciency of the steam in the locomotive 

 is more than double that obtained by the best condensing engines, more than 

 treble that derived from stationary non-condensing engines, and equal to the 

 performance of a Cornish expansive engine doing a 50 million duty with a 

 bushel of coals." 



Respecting the experiments of Mr. Nicholas Wood, Mr. Parkes says, (page 

 \29), "The North Star affords a sequence of six experiments at velocities 

 varying from ISj to 38J miles per hour, but the sequence of results is so 

 irregular as to indicate error in two of them, which I have accordingly marked 

 and rejected, for it is certain that a greater measurable effect must accrue 

 from the expenditure of equal power at 25 than at 30, and at 3I3 than at 34 

 miles per hour; yet the reverse appears on the face of the experiments. It 

 is also equally impossible that a greater momentum should have been gene- 

 rated by a like consumption of force at 34 than at 25 miles per hour." 



Respecting the experiments of Mr. Edward ll'oods, with the Hecla, Mr. 

 Parkes says, (page 117), " On turning to the tables, and examining the results 

 of this experiment (case 2), it will be apparent ; 



" I. That a duty has been performed of double the amount effected by the 



condensing engine, with an equal expenditure of power (column 15). 

 " 2. That the absolute force impressed upon tlie pistons, as determined by 

 the relative volumes of water and steam was 3095 lb. per square inch, 

 whereas the tractive efJbrt requisite to overcome the assigned resistance, 

 amounted to 39-28 lb. per square inch, exclusive of the force equivalent 

 to the friction of the loaded engine and blast pressure (cols. 29, 30). 

 " 3. That the power required of the engine to balance the tractive effort 

 alone was 1515 horses, whilst the absolute power furnished by the steam 

 to move the engine, to neutralize the blast resistance, and to overcome 

 the load, amounted only to 119i horses (columns 33, 34). 

 " 4. That the water expended as steam per horse power per hour, was 

 37-89 lb. for the tractive effort or duty only (column 42), whereas the 

 condensing engine consumes 70 lb. per efl'ective horse power. 

 " 5. That compared with a fixed non-condensing engine at equal pressure, 

 the locomotive, though labouring against the heavy counter pressure of 

 the blast, from which the other is free, is assumed to liave performed 

 equal work, with less than one-half the expenditure of power. 

 " Such ar« the incredible results arising out of data purporting to be fairly 

 and uecessarily deduced from impeachable experiments." 



Therefore we were quite justified to say in our former paper, that it was 

 remarkable that in applying his pretended verifications to all the experiments 

 pubhshed on locomotive engines by different engineers, Mr. Parkes had found 

 that the conditions to which he proposed to subject those experiments were 

 not verified in them, and that such a result ought to have put him on his 

 guard agaiust the soundness of his own arguments. But, besides, we have 

 proved that Mr. Parkes has used, iu all bis calculations, velocities wliich are 

 erroneously averaged and greatly exaggerated ; that he has taken no account 

 of the gravity on the different inclinations of the road ; that he has neglected 

 the friction of the engines, the resistance of the air, &c. ; that he has calcu- 



