138 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



[Aprii, 



warehouse of Messrs. Crafts and Stell, and would evidently have been ade- 

 quate, ill (lie same situation, lo produce all the consequences. 



It may be here observed, that the experiments clearly prove, that the heat, 

 iu different parts of the iiipe, is not nuiforni. Generally it is greatest at the 

 highest elevation, where its superior temperature appears to be of the longest 

 duration under ordinary incidental changes. At the commencement of the 

 operation, however, and a .-.liort time after fresh fuel had been applied, the 

 temperature v\as highest in the flow-pipe contiguous to the furnace. Another 

 circumstance, likely to produce au inequaUty of heat, may be adverted to : 

 the tubes i.re far from being of uniform internal diameter ; the consequence 

 of which must be, that as the same quantity of water has lo pass, in the same 

 time, through every part of the ajiparatus, the liquid must move with greater 

 velocity at one place than at another, and thus, from obvious causes, develop 

 a greater quantity of caloric. The difference is sometimes so great in the 

 relative bores of the tubes employed, that in some which were examined, one 

 tube had an internal diameter of !t-16tlis, and another of Jths of an inch, that 

 is to say, in the ratio of three lo four ; or, taking the relative areas or sections 

 of the tubes, which represent the relative quantities of fluid contained in a 

 given length, in the proportion of nine to sixteen. Thus, taking the velocity 

 reciprocally as the section of the pipe, the velocity of the water at one part 

 of the apparatus being icpresented by sixteen feet, the velocity in another 

 part would be nine, or the ia|.iility of the current would be at one place nearly 

 double that which it was at another. 



It is stated, in a work recommending the hot water system, that " the ap- 

 plication of heat fills " the ascending or flow-pipe " with minute bubbles of 

 steam which rise rapidly to the upper part of the tube, aud become there con- 

 densed into water again :'' now, as condensed steam, wherever it occurs, 

 produces about seven times as much heat as the same quantity of water at 

 the same temperature, we have, at once, a reason for the heat of the pipe 

 being generally greater at a distance from the furuace tbau contiguous to it. 

 This apparent anomaly, wliich has been repeatedly observed and denied, ad- 

 mits, therefore, of an ca.sy explanation. 



The explosion may, under different circumstances, occur from various 

 causes. 



1. As water expands in bulk about five per cent, from 40', its point of 

 greatest density, to 212', the boiling point, the expansion must be very con- 

 siderably more when raised to high temperatures. If, therefore, the pipes be 

 nearly filled with water, aud the expansion pipe not adequate or iu proper 

 condition, an explosion must be inevitable. Dr. Graham states, that, from 

 freezing to boiling water, the expansion is from 22.70 to 23- 7G = 100 to 104-4 

 nearly . 



2. The conversion of the water into vapour, producing an expansion which 

 is in the proportion of a pint of water changed into 210 gallons of steam, 

 " with a mechanical force sufficient to raise a weight of 37 tons a foot high," 

 must present a pressure upon the tubes sufficient to ensure their destruction. 

 Dr. Graham makes a cubic inch of water to expand into 1,604 cubic inches 

 of steam, or one pint of water to become nearly 212 gallons. 



3. It has been observed, as an ordinary occurrence, by those much accus- 

 tomed to the apparatus, that, in some cases, a quantity of gas is generated, 

 and has been found to escape, in considerable quantity, when au aperture is 

 made in the upper part of the pipes. The only gases which could be thus 

 obtained are the elements of the water, oxygen and hydrogen. The former 

 would probably be taken up in the oxydation of (lie metal. Now the hydro- 

 gen gas, which would remain, has never been deprived of its elasticity, and 

 never made to change its state, by any compressing force hitherto applied. It 

 is obvious, therefore, that inevitable danger must arise from its production. 

 It may be worth wliile to remark, that aij-, steam, and hydrogen gas expand 

 in the same proportion by augmentatious of temperature. The law discovered 

 at the same time, and by independent methods of experiment, arose out of 

 the researches of Dr. Dalton and M.GayLnssac. It may be thus expressed: 

 Aeriform bodies expand the l-480th part" of their bulk on the addition of each 

 degree of temperature. Thus, taking 480 cubic inches of steam or hydrogen 

 gas at 32', the itass becomes, at 33% 481 cidiic inches ; at 34°, 482, cubic 

 inches : and so on : or, in a general fonu, a bulk a raised d^ of temperature 



becomes a + . 



480 



4. The last source of explosion to which it is necessary to refer, ainses 

 from any casual impediment in the piiies ; and it freely admitted, that in frosty 

 weather such an impediment is likely to occur ; it has been found to residt 

 from other causes, as in the case of extraneous matter accidentally getting 

 into the pipes, an example of which was recently presented in the establish- 

 ment of Messrs. Wood anil Westheads. 



In a very obhging letter received, in the course of the investigation, from 

 Sir Robert Smirke, it is stated, that, thougli he has " never seen the pipes 

 heated sutlicieutly to ignite wood, except on one occasion," yet, " if a tire is 

 incautiously made when there if a stoppage in the pipes from frost or other 

 accidental cause, the pipe within the furnace may be hurst or made red hot 

 near the furnace. 1 have known the pipe," he adds, " so heated only iu one 

 instance, when the red heat extended to a distance of upwards of 12 feet from 

 the furnace." 



Sur Robert concludes his letter by suggesting a protective modification of 

 the apjiaratu.^. " Therefore," he observes, " to prevent the risk of tire to a 

 building, 1 wotild never place the furnace in a room or cellar that is not fire 

 proof, nor would I have the pipes iu any part of their circuit iii actuttl contact 



with wood or other combustible material. Security,' he continues, " is still 

 more effectually attained by having a safety-valve upon the pipe near the fur- 

 nace, by which explosion or excess of heat wonld be prevented." 



That which has hapjiened once, may, under the same circumstances, happen 

 again. The exclusion from actual contact with combustible materials, could 

 it be permanently ensured, would, when the red heat extended along the pipe 

 upwards of twelve feet, afford, at least, very reasonable grounds for appre- 

 hension. 



On this system of warming buildings, therefore, danger must be produced 

 from either negligence in the feeding of the furnace, or any stoppage in the 

 pipes : the former evil may be obviated by proper precautions ; but the latter, 

 occurring unexpectedly, exists unobserved, and precaution and care must be 

 equally unavailing." 



Signed, John D.wies, 



George Vardon Bydkr. 



^fal■c/l 10, 1841. 



ON THE STYLE OF WREN. 



FoLLOwixG in the train of Palladian arcliitects comes Wren, another 

 of the school, though exercising its sentiments in a different way. He 

 took from Palladio the idea of modi6cations, as also he learned from 

 Jones the art of distribution ; but then, he also learned a something 

 of the sentiment of English architecture, and so fashioned a style com- 

 pounded of them all. Not that he deviated from classic rule, or in- 

 dulged in a detail inconsistent with the whole. This Wren could not 

 do. But inasmuch as the broad masses of Palladio and Jones, were to 

 be sacrificed to the more modest limits of ecclesiastical structures, he 

 had to prepare his features for altitude rather than for breadth. In- 

 stead of the artist having to lead the eye upward, he had now to pre- 

 vent its too hasty ascent, and had to enchain the fancy here or there, 

 as if to compel the eye to wander where otherwise it would instantly 

 soar. In him we see the first architect of his school for beauty of 

 outline and simple elegance of form. Iu Jones we view the artist 

 more in his dispositions of efiect, more in the skilful appropriation of 

 the parts, than in the finished elegance of the parts themselves. In 

 Wren we see more justness of expression, more attention to parts, 

 and richness more tempered with chastity. Jones was the master, 

 natural and often carelessly so, Wren was tlie master, designing more 

 by principles, and adjusting leading objects ere the richness of orna- 

 ment appeared. Jones seemed to delight in masses of light and shade, 

 in bold contrasts, in feeling touches. Wren allowed tae' orra of a 

 part to display its dignity, and allowed the contrast to appear in 

 changing outlines. Both took their lesson from Palladio, but Wren 

 studied symnietiy the most. Jones took Palladio's errors and revived 

 them; Wren improved upon both in the outline. He took also from 

 the antique to improve, as he also bonowed from Michael Angelo to 

 surpass him. 



Besides this, Wren was the first to bend Roman architecture into 

 the poetry of the Christian without violence to either. This idea 

 springing up on the decline of Roman art, and differently exhibited at 

 later periods and in the middle ages, was perfected by liim until classic 

 orders and figures tapered into every variety of elegance. But the 

 spirit of design in Wren was different from that in the olden times. 

 A departure from Roman precedent was then an innovation, iu which 

 the puiity of Roman detail was sacn/ced to new forms and increasing 

 altitude, whereas Wren on the contrary, on the restoration of the Ba- 

 silica, caught the poetry of the monks only to give life aud richness to 

 Roman grandeur. Wren's great aim was to give the eye a succession 

 of pyramidal objects, the moment those objects were separated from 

 the mass ; there is otherwise a repose and solemn dignity about the 

 lower parts of his edifice. To carry out this idea involved a variety 

 of figures and a change of ornament, which became as essential to the 

 line of ascent as necessary to enrich. The line of ascent is never 

 broken; .the eye easily advances, whilst, as it advances, a change as 

 consistent as various appears to meet it. In St. Paul's there is a total 

 contrast between the lower part and the superstructure. In St. Peter's 

 there is a breadth of parts about the superstructure unrelieved, [n 

 St. Paul's the horizontal lines growing gradually less prominent to- 

 wards the dome terminate into sweeping perpendiculars. In St. 

 Peter's the horizontal is never sacrificed for a moment. Iu St. Paul's 

 the objects multiply iu proportion to the height, as also parts get 

 smaller, that is, divisions and subdivisions of parts appear, whilst each 

 grows narrower and more towards a pyramid. Where Wren grew in 

 endless variety, the architects of St. Peter's only tamely ascended. 



Wren therefore was the first who whilst he spread grandeur and 

 massive repose beneath, drew the eye by a thousand artificies into the 

 more pleasing beauties above. 



If Palladio gave the same spirited outline to the basilica, Wre 



