1839.] 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



473 



'f it appear tliat they are of the kiuJ supposed by Capt. Fitzroy, it will bo 

 very necessary to call upon mallicraaticians to altempt llie solution of the 

 byilroilynamic problem, either in a rigorous or an approximate shape. 



Oil the Specific Gravity or Dcmittj of Steam at successive Temperatures, by 

 Dr. Ure. 



This Report was made agreeably to a motion at Newcastle, calling on Dr. 

 Ure, Mr. Faraday, Mr. B. Donkin, and Mr. Cooper, to draw up a view of the 

 present state of our know)edf,'e upon that subject. The other members of 

 the Committee having declined to enter upon the reseai-ch, Dr. Ure undertook 

 it. He began his Report by stating that M. Gay-Lu.ssac was the first phi- 

 losopher who devised and executed an exact process for determining the spe- 

 cific gravity of steam and other vapours ; his principle being to measure the 

 volume of vapour furnished by a given weight of litittid. Having weighed a 

 glass bulb, lil<e that of a thermometer, he tilled it. by healing it, and plunging 

 the point of its capillary tube in the liquid to be converted into vapour ; re- 

 peating the heating and immersion till it was perfectly full. It was now 

 slightly heated, to expel a drop of the liquid from the point, which was then 

 hermetically sealed by the blowpipe. 'J he bulb was next introduced into a 

 graduated bell-shaped jar. about one foot long, and two inches in diameter, 

 filled with and inverted over mercury, in a cast-iron pan. The jar was sur- 

 rounded by a glass cylinder, open at each end ; and the space betHecn tlic 

 two vessels was filled with oil, or water, according to the volatility of tlie 

 liquid. The interstitial column of liquid rested upon the column of mercury 

 in the iron basin or pan. This was placed over a little furnace, w hereby the 

 mercury and superjacent oil were heated to any desired pitch. Eventually 

 the bath became hot enough to generate vapour of such tension within the 

 bulb, as to burst the thin glass of which it was blown. In the case of water, 

 M. Gay-Lussac continued to heat the apparatus, till the water contained be- 

 tween the two cylinders had entered into a state of steady ebullition ; and he 

 then measuJed the space occupied by the steam generatod from the bulb in 

 the bell jar, taking care to note the height of the quicksilver within the jar 

 above its level in the ba.sin Deducting this height from that of the barome- 

 ter in the same apartment, he Ibund the pres.sure of the internal vapour. He 

 then reduced, by calculation, the length of the mcrciu'ial column to w hat it 

 would have lieen at the temperatiu'c of melting ice ; and made a small cor- 

 rection for the height of the liquid column between the two cylinders. In 

 this research, we must take care that the w hole of the liquid in the bulb is 

 reduced into vapour, otherwise we sliall fall into great errors. Tliis circum- 

 stance would occur if more liquid were introduced into the bulb than would 

 fill the whole space over the mercury in the bell jar, at the given tempera- 

 ture. M. Gay-Lussac founil in this way, that one cid-iic inch, or a gramme 

 measure of w ater, produced 1 ,691 cubic inches, or gramme measures, of steam, 

 at the temperature of 100 Cent, or 212° Fah., under a pressure of 29,012 

 inches of mercury, or that of the atmosphere in the mean state of the baro- 

 meter, lie reduced that v(dume to what it would be at 32° Fah., by the rule 

 for estimating the expansion of gaseous matter by heat, and concluded that 

 the specific g'ravity of the vapour of water was to that of air, both at the 

 said temjierature, as ()2o to 1000. The following table of densities includes 

 all the vapours which he subjected to experiment upon that occasion : — 

 Air (as 0° Cent.) being called . , . 1000 



Vapour of Mater . . . . .0 625 



Alcohol ...... 1-613 



Sulphuric Ether , . . . . 2 586 



Sulphuret of Carbon .... 2 645 



Oil of Turpentine ..... 5013 



The density of the vapour is evidently irrelative of the boiling point, o^ 

 density of the liquid from which it is lormed ; for clher boils at 98° Fah.' 

 and has a specific gr.ivity of 0"00 or somewhat less, w hilc oil of turpentine 

 boils at 316 Fah., and has a specific gravity of 0'870. 



Tlie steam which issues from the spout of a tea-kettle is no hotter, as mea- 

 sured by a thermometer, than the boiling liquid within, and yet, wlicn con- 

 densed in a body of colil ivater or ice. it gives out as much heat as one thmi- 

 sand times its weight of boiling water would do. This heat of steam, wluch 

 is insensible to the thermometer, is called latent heat, and it dill'ers in quan- 

 tity fordiflerent kinds of vapour. One part of water at 212° Fah. requires 

 for its conversion into steam, as much heat as would raise SJ parts from the 

 freezing to the boiling temperature, or as would heat it up to IITO"' Fah., 

 could the water be made to receive that heat without changing its form. The 

 (|uantity or energy of heat which steam contains or possesses is constant ; 

 that is, for equal weights, steam of every temperature and density contains 

 the like cjuantity of heat ; — a proposition which has been proved by accurate 

 researches. Water at all temperatures, even in the state of ice. is convertible 

 into vapour : the density of this vapour depends upon its temperature; so 

 that this density, that is, the weight of the steam under a given volume, is 

 greater the higher the temperature at wdiich the steam is generated over 

 water. M'hen the steam is not in contact with water, it follows the same 

 law of expansion with heat, as gases do. An air-tight boiler having a vacant 

 space over the water of about 1,700 cubic inches, contains at the temperature 

 of 212°, one cubic inch of w ater in the state of vapour, and has therefore a 

 specific gravity of .3-000589; water being 1-000000: = ■ ''°!^'" - " . If the 

 heat be raised to '234'5°, the incumbent steam will acquire an elastic force 

 e(|ual to ioi inches of mercury, or 22 3 lb. upon the square inch, and a den- 

 sity of 0000867 ; if to 2502°. ihe elastic force w ill be 59-8inches of merciuy, 

 or'29-26 pounds, and the density will be 0001114. In the fomier case, the 

 elasticity has increased about 50 per cent., and the density 34-3 ; in the latter 

 case the elasticity has increased another 50 per cent., and the density 32 1 : 

 thus, while the elastic force is doubled, the density is increased in the pro- 

 portion of 111 !■ to 589 or 100 to 53. M'e see, therefore, that the elasticity of 

 steam increases with the density, but in a greater proportion, or more rapid 

 ratio. Since like weights of steam conhain like quanliiies of heat, and since 

 the elastic force of steam is the moving po'.vcr in s'eim-engines, it follows, 

 that for like quantities of lie.it, or fuel well applied, a greater elfcct w-ill be 

 obtained from steam of high temperature and density, than from steam of 



low-er temperature and density. At all temperatures, the sum of the latent 

 and sensible heats of steam is a constant quantity, so that steam of higher 

 density and temperature contains always the same quantity of heat, as steam 

 of loH-er density and temperature. M'hen denser steam flows into a vacuous 

 space, it will fill it entirely without condensation, provided that no heat is 

 dissipatcvl outwards; and it will possess an elasticity and temperature de- 

 pendent ujnm its expansion. ,Suppo.'^e, for example, that a vessel of one cubic 

 foot capacity is filled with steam of 212° Fah.. let this vessel be placed in 

 communication wdth another air-tight vessel, of nine cubic le"t capacity, so 

 as to expand into it ; in filling the latter, it will become cxjianded into ten 

 times its bulk, and from the table ^vbich accompanies the report, it will be 

 iound to assume, when thus e.spanded, a temperature of 108.5° Fah., while its 

 elasticity falls to 2-4 inches cl^ mercury ; though the steam has neither ab- 

 sorbed nor emitted any heat, nor deposited any water by condensation. 

 A\'hcn dense steam escapes into the air, it assumes the same specific gravity 

 and elasticity as the atmospheric vapour. 



'I'he talde annexed contained seven columns ; the first three were the scales 

 of the three thermometers now in use ; and Dr. Ure remarked, that it was to 

 be regretted, that we in Great Britain do not adopt the Centigrade scale, as 

 the Germans are now doing, instead of the arbitrary and inconvenient divi- 

 sions of Fahrenheit. The fonrtli and fifth cidumns exhibited the elastic forces 

 of the steam, the former in inches of mercury, the latter in pounds upon the 

 square inch. The sixth column showed the number of cubic feet of steam 

 resulting from one p<iund of water, and the seventh the specific gravity of 

 the steam, water being called unity, or I'OOOOOO. 



COMPETITION DESIGNS FOR THE ROYAL EXCHANGE. 



We need not particularly regret our inability at present to entei 

 into the various questions which this competition suggests to us, siuce 

 we foresee that whatever turn matters may take, we shall have more 

 than one opportunity of making our comments before the business is 

 settled, or any thing- finally determined upon. As far as we can under- 

 stand, that is, as far as on-dUs may be relied on, all the three archi- 

 tects who g.ive in their report on the designs to tlie committee, have 

 now declined taking any farther sliare in the affair ; nor do we wonder 

 that they have done so, since the task tliey were called upon to un- 

 dertake, woidd have been as invidious as it would have proved difH- 

 cult; — and that it would have been a difficult one, can hardly be 

 disputed without calling their sincerity into question, there not being 

 a single design which they could recommend to be returned to its 

 author, in order that he might make those corrections whicli would 

 remove the first objections to it. Their non-coinpliauce with the 

 committee's recpiestjonly confirms whatever was previously expressed 

 in regard to it. But what course the committee will now take, we 

 are unable to conjecture, our surmises extending no farther than to 

 giving them credit, for at length discovering how ill-advisedly 

 they have acted throughout the whole business. 



Among other things, they have probably now found out that it 

 would have been infinitely more prudent on their part to have had a 

 public exhibition beforehand, and one of such duration as to afTord 

 time for people to form something better than hurried, otl'-hand 

 opinions. And if it be -asked where such protracted exhibition could 

 have taken place, without causing inconvenience, we sliould say that 

 perhaps, no fitter place could have been found th-.mthe exliibition rooms 

 of the Royal Academy, where there would have been space to arrange 

 all drawings, without hanging any of them up so high as they were 

 at Mercer's Hall. And we must say, that it would have been no more 

 than natural and proper, had the academy offered their rooms for that 

 purpose ; — or are we to presume that the whole alRiir is matter of 

 utter indifference to that body ; and that though it is one which may 

 eventually bring credit or discredit upon the taste of the country, the 

 academy are not willing to give themselves the least concern about 

 it. It cannot be said that, by taking no notice in any way of what 

 does not immediately relate to them, the academy can be charged 

 with having neglected their tluty, yet tlie fact itself is a symptom of 

 the zeal with which they are animated for advancing art and its in- 

 terests generally. 



Undoubtedly a very great point in architectural competitions has 

 been secured, by the public being allowed to see the designs at -all, 

 though, in the case of that for the Royal Exchange, the exhibition 

 was no more than what is generally styled a private etcw. Still in this 

 respect, another point remains to be carried, which is, that in future 

 all such exhibitions shall be j'Klimiiiari/ : nut in order that umpires 

 and committees should be entirely guided by, or pay untpialified de- 

 ference to a majority of opinions so elicited, but that they may have 

 the opportunity of taking into consideration wliate\cr arguments, if 

 any at all may happen to have been brought forwartl, on various 

 points. We therefore trust, that instead of this competition, and 

 the one for the Nelson monument being- made use of to show the 

 utility of public exhibitions of the designs, tliey will opei-ate as use- 

 ful corrective lessons, and li'iul henceforth to the ;idoption of a better 

 system. 



2 T 2 



