134 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



[April, 



him to assert that she had only " coal enough for the trip, and no stores, 

 and made 1 7 strokes per minute."* 



It happens also, unfortunately for " Vulcan's" veracity, that the engines on 

 the Gorgon principle liave an arrangement to equalize their action, and 

 balance the effect of the weight of the piston and its appendages ; and that 

 this moreover is not done by the means of weights upon the paddle -wheels. 



Those parts of the letter which treat of the " miserable inefficiency" of the 

 " Government folks," who are stated to be so " far behind private knowledge 

 and enterprise," and much of the same description, are worthy of a virulent 

 scribe in an opposition newspaper : but as I should be very sorn- to see your 

 magazine made an arena for political discussion, " Vulcan" is very welcome, 

 for me, to continue his tirade against the Government at his pleasure. He 

 cannot deny that the .\dmiralty have given a decided preference to the direct 

 form of engine, or he would doubtless be glad enough to do so ; if he chooses 

 to go upon another tack, and ascribe this line of conduct to their ignorance 

 or their unjust partiality, it is of course with " my lords" that he has cause 

 of quarrel, and not with the Gorgon engine.f 



The " prophecy" with which the paper concludes will be upon record, and 

 to it " Vulcan" may refer, in proof of his own sagacity and foresight, when 

 he finds the Gorgon engines removed for inefficiency ; but at present, while 

 some of the vessels thus fitted are amongst the fastest sailers of their class, 

 and while their superior adaptation for war purposes is proved by their 

 services in actual engagement, (to which "Vulcan" bears such reluctant 

 testimony,) we may safely conclude that the day of "Vulcan's" glorification 

 as a true prophet will be yet far, far distant. 



I am, Sir, 



Bloomsbury, Yours obediently, 



Fei., 1842. AVilliam Pole. 



MR. JOSIAH PARKES AND THE COUNT DE P.4MB0UR. 



SiK — In a letter inserted in your number for last October, Mr. Josiah 

 P arkes has brought forward two grave charges against M. de Parabour : first, of 

 " gross and lamentable ignorance of practical matters," founded upon a 

 passage from this author's "New Theory of the Steam Engine;" secondly, 

 of having misrepresented and falsified certain of Mr. Parkes's opinions and 

 writings. The latter of these charges the Count has already sufiiciently 

 defended himself from, but the former he has left unnoticed, doubtless under 

 the supposition that its groundlessness and absurdity must be so self-evident, 

 as to render a formal refutation unnecessary. This may perhaps be the case, 

 as far as those are concerned who are well acquainted with the subject on 

 which the charge is founded ; but it is probable there are many who, for want 

 of information, may be inclined to construe the silence of Count de Pambour 

 into an inability to deny the truth of the allegation, and I think it but com- 

 mon fairness that such should be shown the true state of the case. I should 

 blush for Enghsh engineers, if there could not be found among us some 

 liberal enough to defend from such ungenerous attacks as these, a dis- 

 tinguished foreigner who has, on connecting himself more immediately with 

 our country, laudably devoted his time and talents to the advancement of 

 our scientific knowledge. 



M. de Pambour's passage is as follows: — "Under this circumstance (the 

 use of the cataract,) the engine does not evaporate the full quantity of water 

 that its boiler would otherwise be capable of evaporating per minute." Mr. 

 Parkes cites this to show the " gross ignorance" it displays, adding that 

 " neither the Cornish, nor any other engineers ever, probably, imagined the 

 cataract to exercise an influence over the production of steam in the boilers 

 of their engines. 



' Now the following facts cannot, I am sure, be denied by any one at all 

 acquainted with the working of Cornish engines. 



Isf. The use of the cataract determines the number of strokes to be made 

 by the engine in any given time. 



2nd. No steam being ever allowed, in Cornwall, to blow away at the 

 safety valve, the quantity produced is necessarily only what is used. 



3rd. The quantity used depends (ceteris paribusj upon the number of 

 strokes made by the engine in a given time. 



'■ See Journal for June ast, p. 210, Vol. IV. 



r Since writing the above, il has come to my knowledge that an order for 

 eight pairs of engines, upon the direrf action principle, of 400 (o 500 horse 

 power each, has been decided upon by the " Government folks," and this 

 with ■' Vulcan's" paper before their eyes! 



4th. From which it must follow, if there be any meaning in words, that 

 " the use of the cataract" does " exercise an influence over" the quantity of 

 steam used, and consequently over "the production of steam in the boilers." 



And of course when the cataract is so arranged as to cause the engine to 

 make less than its maximum number of strokes per minute, (which is 

 generally the actual state of things,) it must be evident that " under this 

 circumstance the engine does not evaporate the full quantity of water that 

 its boiler would otherwise be capable of evaporating per minute." 



Mr. Parkes either knew these facts, or he did not. If he did, he lies under 

 the imputation of having brought a charge against M. de Pambour which his 

 reasoning powers must have told him, had he exercised them at all, he could 

 not substantiate. If he did not, on which side does the " gross ignorance" 

 lie .' I can tell Mr. Parkes, that many persor.s of, perhaps, equal knowledge 

 and skill with himself, are ready to plead guilty to an association with M. de 

 Pambour in his " ignorance," if such it be. 



But is Mr. Parkes liimself perfectly immaculate, touching this cat.iract ? 

 He says, " The cataract is used for the purpose of opening the steam indue 

 tion valve, and its value is appreciated as a means of effecting the influx of 

 steam into the cylinder in the most instantaneous manner." Again, in his 

 second paper on the percussive action of steam, published in the 3rd volume 

 of the Trans. Inst. C. E., (Note E, p. 430,) we find, " No apparatus for open- 

 ing steam valves with rapidity, and, therefore, for letting loose the steam 

 upon the piston of an engine, with the full velocity due to the difference of 

 the elasticities existing in the boiler and in the cylinder, has yet been applied 

 so effective as the cataract." 



Now, as it happens, the cataract does not open the steam valve at all, 

 except on the " House-that-Jack-built" principle. It only removes a catch, 

 which lets fall a weight, which opens the valve, and effects, &c. The removal 

 of the catch, which is all the cataract does, might be done just as well by 

 the plug rod, or by band, or by a thousand other contrivances, as by the 

 cataract. It is the fall of the teeiglit which effects the instantaneous open- 

 ing ; and therefore what merit can belong to the cataract on this score, it is 

 not easy to see. It might as well be said to be valuable as a means of pump- 

 ing the water from the mine, for it is quite as much instrumental to one as 

 to the other. 



It would have been well had Mr. Parkes removed this " beam from his 

 own eye," before he began to find fault with the " mote" in M. de Pambour's. 



I remain, Sir, 



London, Yours, with respect, 



Feb. 1842. Vindicator. 



ON THE FORCE OF FALLING BODIES, AND PILE-DrvIVING. 



SiK— In the Journal for last month, after the description of the " American 

 Steam Pile-driving Machine" with which you favoured your readers, there 

 are some judicious remarks on " the force of the blow given by the ram 



of a pile engine," and a table calculated from the formula 32^ Ay' j^^ 



for finding the velocity of a body falling from the height s, for the force in 

 tons ; the weight of the falling body being one ton. Now it appears to me, 

 from want of defining an unit of force, and the force in tons therein given, 

 this table may be mistaken for a mere weight acting by pressure without any 

 velocity, by persons not acquainted with the principles from which it is 

 derived. Would it not, therefore, be well to define the unit of force, as you 

 have taken it, to be the weight of the ram moving with a velocity of one foot 

 per second .' In page 255, Vol. II., July, 1839, concluding some remarks on 

 this subject, I gave an example founded on the above principles, that is, 

 taking the force used in driving the piles as the weight multiplied by the 

 velocity, and comparing this with the weight of the superstructure, supposed 

 also to be for the comparison a moving force. 



In the Mechanics' Magazine for December 30, 1836, No. 175, a cor- 

 respondent, in answer to a question on pile-driving, says the force of a ram 

 falling from a height of 1} inches is double its weight, and a correspondent, 

 B, in your Journal for August, 1839, states from some experiments on a spring 

 balance, that one-half the weight, falling with a velocity of f foot per second, 

 is equal to the weight in effect j which is to say, that the whole weight 

 moving with a velocity of § foot per second, produces an effect equal to twice 

 the weight of the body. A body falling from the height 1} inches acquires, 

 after descending that height, a velocity of 2-6 feet per second. This would. 



