1841.] 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



375 



his 3rd example, wlipre the steam is (supposed to be) cut off at 5*2 

 inches from the commencement of the stroke, the diminution of tem- 

 perature would, with that expansion, amount to about 80 degrees; 

 but this is much greater than it would be in reality, on the hypotheses 

 made by Mr. Lawrie, because the values found by him for (a ) and (b) 

 are so much too small as to exaggerate the expansion enormously ; 

 as an inst.nce of which, in the example just quoted, tliese valves 

 ought to be 0-7726 and 0-9259 respectively, instead of 0-2884 and 0-7, 

 and the steam would consequently be cut off" at 13-9 inches, instead of 

 6-2, from the commencement of the stroke. This error, which runs 

 through all 4 examples, and thus vitiates all the deductions, arose 

 from Mr. Lawrie inadvertently changing the unity from the radius of 

 the eccentric to the width of the port, in applying his formula. 



Mr. Lawrie says that, when I objected to the omission of the effect 

 of the steam during the part of the stroke from the opening of the 

 eduction port to the termination of the stroke, I ought to have told 

 you what degree of expansion I alluded to, as that altogether decides 

 the extent of diminution of pressure by expansion. This is sufficient 

 reason for not neglecting the quantity in question ; for if there is any 

 degree of expansion for which it ought not to be neglected, the only 

 way to be sure of not doing so in that particular case is to include it 

 in the general formula. However, I will take Mr. Lawrie's 2nd ex- 

 ample, where the lead (on the steam side) is ^ of the breadth of the 

 port, and the cover (also on the steam side), i breadth of port. Mr. 

 Lawrie assumes that the valve has no cover on the eduction side of 

 the port, which I think he will not find to be exactly the case ; Mr. R. 

 Stephenson allows -j-j inch on each side, and the ports are only 1 inch 

 wide, which makes the cover on the eduction as well as the steam 

 side of the port, -'^ of its width. It is obvious tliat this arrangement 

 causes the eduction to commence later, by which means the pressure 

 of the steam is not reduced so low at the end of the working stroke 

 as it would otherwise be. It is, however, with the conditions assumed 

 by Mr. Lawrie that I have calculated, at a great cost of time and 

 labour, what the diminution of pressure would be in this example, 

 from the opening of the eduction passage to the end of the stroke. 

 I have supposed the initial pressure (before expansion) to be 5 atmos- 

 pheres or 73-53 tb. per square inch, and the total area of the port ^ 

 that of the piston, and I have purposely made the reduction of pres- 

 sure come to more, rather than less, than it would really amount to. 



The radius of the eccentric, or i the travel of the valve, which is 

 called unity in the formulae for calculating (a') (6) and (c'), is equal to 

 the width of the port -\- the cover = J width of port, whence the 

 width of port =: f, and i =: ^, c = i. With the aid of these values 

 we find a' ■=. 0-8482, 6 ^= 0-9479. Neglecting the waste space, the 

 pressure is reduced by expansion to 65-07 lb. The eduction lead = 

 the lead ■\- the cover on the steam side = f width of port, which is 

 the extent of opening to eduction at the end of the stroke ; and the 

 crank is 26° 23' 16" from the dead centre when the port begins to 

 open. This I have divided into intervals of 1°, and have computed 

 tlie discharge of steam during each interval, supposing it due to the 

 difference between the pressure at the beginning of the interval and the 

 pressure of the atmosphere. This calculation is consequently very 

 long, but I believe there is no formula yet discovered which gives the 

 discharge during the whole time at once. I found in this manner that 

 the pressure would be reduced at the end of the stroke to 52-8711)., or 

 38-16lf). above the atmosphere, which gives a mean pressure during 

 the eduction lead of at least 44-26tt). per square inch, or distributed 

 through the whole length of the stroke, 2-3 1ft. This, I think, Mr. 

 Lawrie will net call tncomidcrable ; while the effect of compression 

 would certainly not surpass, if equal, 0-41t). per square inch through 

 the stroke, which I consider rather to be neglected than the former. 



I shall conclude my letter with showing, as I stated above, that the 

 corrections I introduced into the value of (s) are not altogether to be 

 neglected, and for that I shall apply them to the example chosen 

 above. Qy Mr. Laivrie's formula, we have 



s = = 1-193G. 



4-241—1 -f 0-9479 



By the corrected formula, making 2 rf= 1, 5 r= 1, 5 := 4-3057, ra = 

 0-05, we have 



— 4-3657 + 0-1633 _ 



■' — 3-703 — 0-0521 + 0-1683 ~ ' ' ' 

 The difference is certainly not very considerable, being only about 

 I per cent, on the required area: but v\hy should even that correction 

 be omitted, when it can be applied without any ditEculty and «ith 

 scarcely any additional trouble? 



I am, Sir, vour obedient servant, 



M. 

 Ociobtr 14, 1841, 



CROSBY-PLACE, BISHOPSGATE STREET. 



The committee appointed to superintend the restoration of this 

 most interesting specimen of ancient domestic architecture appear to 

 have brought their labours nearly to a close, and an inspection of the 

 result of those labours will secure the praise of every lover of our 

 architectural antiquities. It is highly gratifying to witness the timely 

 preservation of a building which is " the only example of any magni- 

 tude of the halls and places of our forefathers in the metropolis, the 

 numerous other buildings of this nature which once gr.iced the city 

 having fallen victims to the great fire, or the no less destructive hand 

 of innovation. The reparation appears to have been carried forward 

 as far as is desirable until the particular use to which the hall is to be 

 hereafter applied shall be ascertained ; and most fervently do we hope 

 that it may be such as shall best accord with its present beauty and 

 its past historv. The new materials and workmanship harmonize so 

 thoroughlv with the original, as to render it impossible, except on the 

 minutest inspection, to distinguish between the new and the old. The 

 matchless beauty of the roof in the hall has been effectually preserved. 

 This unique specimen of timber-work is remarkable for the skilful 

 omission of ties and hammer-beams. It is divided into eight principal 

 compartments in length, and four in breadth, the points of intersection 

 being ornamented with light and graceful pendants, pierced with small 

 niches, each pendant forming the centre of four arches, so that from 

 whateier point it is viewed the eye is presented with a series of arches 

 of elegant construction. The principal timbers are richly decorated 

 with bosses of foliage, and "spring from octangular corbels of stone." 

 It is remarked that the low pointed arch, approaching to an ellipse, is 

 admirably calculated for the dissemination of sound. " The shafted 

 oriel," notwithstanding all the rough usage to which it has been ex- 

 posed, has recovered its pristine beauty, and, as well as the other 

 windows, is "richly dight" with the s'ained glass armorial bearings 

 of the former proprietors, and of the various companies and individuals 

 of whose munificence the hall itse'.f will be the lasting memorial. 

 From some sources, of which we are ignorant, the council chamber 

 and throne-roora have been restored to a state of great beauty ; not, 

 indeed, on the same scale of magnificence as the hall, to which alone 

 the pulalic subscriptions have been devoted, but yet in a style perfectly 

 in keeping with the age and character of the structure. When Cros- 

 by-place shall be transferred to the hands of its next possessors, these 

 rooms will probably receive all those rich decorations which will en- 

 able them to vie with the splendour of a hall. It is, however, from 

 its historical associations that Crosby-place must ever derive its 

 greatest value and interest. In the reign of Edward IV., it was the 

 magnificent home of Sir John Crosby, its reputed builder, who was 

 here probably honoured with the presence of that Monarch whose cause 

 had been so greatly strengthened by the zeal and prudence of his 

 princely host. It is well known to have been afterwards the abode of 

 Richard IIL ; Shakspeare has immortalized the fact, so that "Richard, 

 Shakspeare, and Crosby-place, must ever be identified." Here Sir 

 Bartholomew Read, Mayor of London, entertained a solemn embassy 

 from Maximilian, Emperor of Germany, of which Lord Cassimir, Mar- 

 quis of Brandenburg, his cousin, accompanied with a bishop, an earl, 

 and a great number of gentlemen well- appareled, was principal em- 

 bassador, which were triumphantly received in London, and were 

 lodged at Crosby-place." Sir Thomas More, the witty and unfortu- 

 nate author of the Utopia, when in favour, occupied Crosby-place, and 

 afterwards sold it to '-his dearest friend" Bouvisi, the Lucca mer- 

 chant. In 1594, it was jiurchased by "the rich Spencer," who died 

 possessed of nearly a million of money, and was an ancestor of the 

 present Marquis of Northa\npton. Here he entertained no less a per- 

 sonage than the Duke of Sully, the Ambassador of Heury IV. of France. 

 Among the sub-tenants in the early part of the 17th century, we find a 

 name immortalized bv Ben Jonson's most beautiful epitaph, "Sidney's 

 sister, Pembroke's mother," and William Russell, probably a scion of 

 the noble house of Bedford. In the disastrous period of the civil wars 

 it was used as a prison for the Royalists; and in 1662, the Reverend 

 Thomas Watson was the first ejected minister who officiated in the 

 hall: he converted it into a Presbyterian meeting-house. He was 

 followed by Stephen Charnock, Dr. Grosvenor, a pujiil of Benjamin 

 Keach, and Edmund Calamv, jun. The congregation continued to 

 meet here till 1769, when it was dispersed, a farewell sermon being 

 preached on the occasion by Mr. Jones, the predecessor of Dr. Collyer, 

 at Peckham. The hall, as every one knows, became subsequently a 

 common warehouse, and fell rapidly into a state of ruinous decay, from 

 which degradation it has now, at length, been recovered. Thus, for 

 nearly four centuries, has this beautiful structure remained, the witness 

 of decent hospitalitv, of boisterous mirth, and of merry wassail; atone 

 time its " rich embowed roof" and arras-covered walls echoing the 



