IS^o.l 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



233 



NEW COVENTRY-STREET, LEICESTER-SQUARE. 



( With an Engraving, Plate XVIII.) 



But for tlie shops along tlie groutul floor, this piece of street arclii- 

 tocliire miglit pass for the facade of some large single edifice ; not 

 that we object to the shops, as shops, and because they are occnpied 

 by persons in trade; but because thev occasion a continuity of open- 

 ings below, that is quite destructive of the appearance of solidity, 

 and that ill accords with the boldness of all the rest. Still we 

 admit the architect hiis done the best which circumstances will 

 allow; fur your shopkeepers are a very self-willed and intracta- 

 ble race in such matters, and insist upon having the utmost possible 

 extent of window. There is more of the appearance of support than 

 usual; and windows do not actually shoot round corners. There is 

 besides a degree of good taste and quietness in the general design of 

 the shops, which we hope will be kept up, by its being conditioned for 

 in the lipases that the tenants sliall not be at libiTty to alter thrir 

 respective fronts at their own discretion (which means discretion with 

 an in before it), nor to do anything at all to destroy uoiformity, out of 

 the amiable ambition of cutting a more dashing appearance than their 

 neighbours, and throwing them into the shade. Overlooking the 

 ground floor, as what cannot fairly be taken into account, and looking 

 only at what is above it, we perceive a marked improvement upon the 

 ordinary system of architectural embellishment for a series of street- 

 houses. It was rather a favourable circumstance than the contrary, 

 that the street itself is so short — a mere avenue opened from Coventry- 

 itreet into the square, so that tlie extent of frontage does not at all 

 exceed that of an ordinary fafade (the length being only 105 feet, 

 and the height GU feet), and loftiness is not overpowered by length. 

 There is, moreover, what is so seldom found in similar cases, the 

 appearance of sutficiency of mass, the elevation being returned on the 

 east and west ends, instead of the design being confined to the mere 

 front, after the fashion of what Punch, or some such malicious varlet, 

 has termed an architectural 'pinafore.' The style here adopted, or 

 we ought perhaps to say introduced, is certainly open to objection 

 from those who make 'has been' the measure and standard of "can 

 be and ought to be," and who disapprove of what does not accord 

 with established autlmrity, knowing that to be at least a safe course. 

 Nor would it be dilTicuit to show, by quoting "bookish dicta," that we 

 ought not to allow ourselves to approve of this design because it 

 smacks terribly of innovation, and is in a composed or mixed, conse- 

 quently in an 'impure' stvle, — one in which elements and ideas bor- 

 rowed from different styles and different modes of the same general 

 style are made to coalesce into something distinct from every one of 

 them. In art the successful becomes the legitimate, and we are well- 

 disposed to accept what Mr. Mayhew has done in new Coventry- 

 street, as a very successful experiment, and a most laudable effort to 

 get us out of the confined and beaten track, which has hitherto been 

 too exclusively pursued. He may be allowed to have "opened up," 

 as the Scotch say, a new one for general street architecture, as distinct 

 from monumental edifices, therefore very well admitting of much 

 greater freedom of treatment. Yet though the style which has been here 

 thus far wrought out, is sufficiently consistent, and well enough applied 

 in this particular instance, the same degree of floridness of character 

 would not be always suitable: on the contrary, might be apt to pall 

 upon the eye in a very extended range of building. There is also 

 great danger of its being overdone and caricatured by second hand 

 copyists; because, unless there be artistic feeling and intelligence of 

 composition, what is meant for decoration is apt to become little 

 better than mere trumpery in unskilful hands. Here, reminiscences of 

 both continental and our own English renaissance are so skilfully 

 wrought into what may be designated by the generic and comprehen- 

 sive term ' Italian architecture,' that the ensemble is sufficiently con- 

 sistent and of a piece. We do not say that it will satisfy those 

 who make simplicity a sine qua non, — an indispensable quality, and 

 what ought also to be the predominating one on every occasion. We 

 too admire simplicity; but we should be very sorry to be able to 

 admire nothing else, as some seem to make a very great merit of 

 doing; for we can even adcnire the very reverse of it when, though 

 there may not be what is generally uciderstood by simplicity, — which, 

 by the by, is frequently quite misunderstood, — there is that correspou- 

 dence of characl r kept up throughout, which arises from the conflu- 

 ence of i<leas all intermingling, and expanding into one stream. Most 

 assuredly there is vi ry far more of the simplicity of unity, and less of 

 mongrelism, in this New Coventry-Street f.i^ade than there is in such 

 a pseudo-tireek design as the east elevation of llie Union Club-house 

 in Trafalgar-square. 



Ko. 95.— Vol. Vlll.— August, 1845. 



THE MECHANICAL PROPERTIES OF AIR AND STEAM. 



We have received a letter from a correspondent who assumes a 

 jocular signature, controverting the accuracy of two papers which we 

 inserted last month, one on " Tin- Properties of Air as a Mechanical 

 Agent," the other on "The Mechanical Theory of Steam proposed by 

 the Artizan Club." We greatly regret that we cannot find room to 

 insert the present letter entire (it extends to 19 pages of note paper), 

 as we are verv anxious to encourage free discussion of scientific sub- 

 jects ; but as a great part of the letter is written in a jocular discur- 

 sive strain, we will insert those parts only which are argumentative, 

 assuring our correspondent that we will not knowingly weaken any of 

 his arguments by omission. In the paper on the Mechanical Proper- 

 ties of Air, he objects to the passage which states that after the pre- 

 liminary exhaustion is complete, and the train-piston in motion, if the 

 rarefaciicm be uniform, " the work done by the prime mover is exactly 

 measured hv the quantilv of motion transferred to the train of car- 

 riages: for every cubic foot of air pumped out at the station, the tra- 

 velling piston describes a foot of space." On this passage our cor- 

 respondent observes, 



Now this assertion of the equality of the work done and the power ex- 

 pended by the prime mover, made liere as an axiom almost too evident to 

 require even to be slated, and on which the whole argument turns, so far 

 from being an axiom is not true, as a very sliglit consideration will show. 

 Suppose, for the sake of easy illustration, thai the the piston of the air pump 

 is the same size and moves at the same sjieed aa the piston attached to the 

 train. This evidently accords with the conililion stated by ■' II. C," that the 

 air discharged must be equal in volume to the space described by the travel- 

 ling piston, and if the equality of power expended by the prime mover and 

 the work done in propelling the train were equal, as stated in his axiom, the 

 constant retarding pressure on the air pump piston ought to be the same as 

 the moving pressure on the travelling piston — the two pistons moving at the 

 same velocity and being of the same area. What is the fact ? Why, that at 

 the beginning of each stroke of the air pump there is no retarding pressure 

 on the piston, the pressure of the air on both sides being equal. From this 

 point till the piston lias made § of the stroke the air is gradually compressed 

 tietween the piston and discharge valve, thus creating a constantly retarding 

 force, which at f of the stroke, and not before, becomes equal to the motive 

 force on the travelling piston. We thus «ec that these two forces, so far 

 from being on the whole exactly balanced, are only in this state during ^ of 

 the stroke; dur ng the other f the retarding power on the air pump piston 

 is much leas tknn the motive power necessary to maintain the motion of the 

 train. 



We hope to be able to convince our correspondent that his objec- 

 tion does not alf'^ct the argument in question. He will observe in the 

 first place that he is assuming the elastic properties of air at rest to 

 be the same as those of air in motion. In a former paper, however, 

 on Atmospheric Traction, referred to in that which our correspondent 

 reviews, it was distinctly laid down that the dvnamical and static 1 

 properties of air are essentially diff'erent. And in accordance with 

 this fact, the pafier of last month concludes by stating that two-thirds 

 —not of the power — but of the slrvkts of the engine are wasted by 

 the preliminary exhaustion. It is difficult to draw a conclusion as to 

 the power wasted, owing to our imperfect knowledge of the properties 

 of air in motion ; but to proceed to a more direct reply, we think we 

 can convince our correspondent that assuming the statical laws of air 

 to obtain, his objection is untenable. 



There are two distinct classes of Fig- !• Fig. 2. 



air-pumps — in the one the upper sur- 

 face of the piston or sucker is open 

 to atmospheric pressure fig. 1, in the 

 other fig. 2, the cylinder in which the 

 piston works is closed at lop, having 

 a centre aperture through which the 

 piston-rod works, and being provided 

 also with a valve opening upwards. 

 Now for the first of these it is obvious 

 that our correspondent's objection 

 cannot apply. The air-pressure after 

 preliminary exhaustion being supposed 



5 lb. to the inch the pressure on a is L— _ A 



Id — 51b. to tlie inch. If a move up- '' 



wards through any distance, say a foot 

 the train-pision will also move through 

 an inch and the pressure on tfiat piston 

 is also 15—5 lb., so that it is clear that 

 for a pump such as fig. 1, the work 

 done anil the power exerted are equal. 



Before however we proceed to fig. 2, 

 we must remark that though in fig. 1 

 the train-piston moves continously forward, the pump-piston lias an 

 alternate action. It is undeniable we think that power expended in 



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