1818.1 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



17 



Example 6. — The stroke of a piston is 36 inches; width of steam 

 port 1"5 inches ; and distance of piston from the end of its stroke, 

 when steam is to be cut off, 7'43 inches: required the lap. 



Heie 7--13 -^ 18 = -ilSl = versed sine of arc 54° 4.'. 

 Then 180° - 54° 4' = 125° 56' ; and 125° 56' -r 2 = 62° 58' = 

 arc of versed sine '5454. 



1 - -545 !■ - -4546; and -4546 -f- -5454 = -8335; 

 ■8335 X 1'5 = 1-25 inches = lap. 



Exhaustion was shown to commence when the piston was at m in 

 its descent, and at s in its ascent ; / and / being tlie corresponding 

 positions of the crank at those times. Now d and/ were the re- 

 spective startinff points of the crank and eccentric; and the arc 

 <1 <jl, described by the crank, is equal to the arc/e/i, described by 

 the eccentric. Therefore, r/ande/ are equal arcs. Hence, 



To find the distance of the piston from the end of its stroke 

 when exhaustion commences, subtract arc the first (found by Rule 

 III.) from 90 degrees, and multiply the versed sine of the re- 

 mainder by half the stroke. The product will he the distance re- 

 quired. 



E^rample 7.— Arc the first (Example 3) = 36° 52' ; and 90° - 

 36° 52' = 53° 8' = arc of versed sine -4 



Then -4x18 = 7*2 inches, the distance required. 



E.ramp/e 8.— Arc the first (Example 4) = 62° 58' ; and 90° - 

 62° 58' = 27° 2' = arc of versed sine -1092. 



Then -1092 X 18 = 1-9656 inches, the distance required. 



From the foregoing examples, it is obvious that whatever may 

 be the relati\e i)r(q)ortions of the length of stroke and width of 

 steam port, the lap must be some multiple of the port, that the 

 steam may be cut off at any given point of the stroke. 



The annexed table exhibits a series of multipliers for determin- 

 ing the amount of lap necessary to cut off the steam at any part 

 of tlie stroke from g th to § ths, when the slide has no lead. 



Muttipliers. 

 'Jtb 14-48 



Portion of the stroke 

 to be performed by 

 the piston before the- 

 steam is cut off. 



Lf 



6-46 

 3-7? 

 2-41 

 1-58 

 1-00 

 •54 



We shall next month proceed to examine the conditions of the 

 slide valve with both " lead and lap." 



R. B. C. 



HEALTH OF TOWNS— THE GOVERNMENT AND 



THE PROFESSION. 



Now that the sanitary movement is likely to hear fruit, it will 

 be well for our professional readers to turn their attention to the 

 share which they are to have in the rewards, after having borne 

 their part of tlie labour. While engineers, architects, and sur- 

 veyors have been working hard in carrying out sanitary reform, 

 in improving the drainage, in reducing the cost of sewers, in miti- 

 gating the smoke nuisance, in warming, in ventilating, in the 

 construction of dwellings, in the application of sewage mantires, 

 and in many other ways, — medical men and members of j)arliament 

 Iiave been making speeches, and claiming the honours of the cam- 

 paign, as it seems they claim the emoluments. AVith what justice 

 members of the constructive professions can be kept out of siglit, 

 we do not know ; but there is a determined set on the part of the 

 medical men to keep them out, and to monopolise the merit and 

 the patronage. Of the five Metropolitan Sanitary Commissioners, 

 two are medical men, viz.. Dr. Southwood Smith and Professor 

 Owen ; and not one is engineer, architect, or surveyor. The com- 

 missioners, at page 51 of their First Report, speak as follo\\s : — 



" It has appealed to be our duty to state, that we have had pre- 

 sented to us ground of exception against one class of appoint- 

 ments to these commissions, namely, that of surveyors, of architects 

 in practice, of builders, traders, agents, and professional persons 

 connected with building operations in their respective districts." 



We think the bias of this passage is readily to be seen, though 

 it does not impugn the appointment of engineers, architects, or 

 surveyors, as paid commissioners, such officers not practising. 

 There is no reason given why an architect and an engineer should 

 not be appointed on the Metropolitan Sanitary Commission in 

 addition to the physician and surgeon, or naturalist. We will 



show afterwards what reason there is why the two former shotdd 

 be appointed. 



The following paragraph of the Report contains an insinuation, 

 well worthy of notice, for it has its object : — • 



" The more the investigation advances, the more is it apparent 

 that the progressive improvement and proper execution of this 

 class of public works, together with the appliances of hydraulic 

 engineering, cannot be reasonably expected to be dealt with inci- 

 dentally, or collaterally to ordinary occupation, or even to con- 

 nected professional pursuits, but require a degree of special study 

 which not only place them beyond the sphere of the discussion of 

 popular administrative bodies, but beyond that of ordinary profes- 

 sional engineering and architectural practice. In justification of 

 this conclusion, and to show the evil of the perverted applications 

 of names of high general professional authority, we might adduce 

 examples of the most defective works which have received their 

 sanction." 



The aim of this is, that the abuse shall he an argument against 

 the use : because some architects have laid down expensive sewers, 

 engineers, architects, and surveyors shall be excluded ; because 

 Professor Donaldson and Mr. Joseph Gwilt approve of the old 

 system, those who have fostered and executed the new system 

 shall not be employed. This is what the commissioners mean, 

 though they do not say it fully ; and we put it to the public 

 whether it is fair to professions, which by their talent and their 

 intelligence have so much contributed to the reputation of the 

 country. 



It may be taken as a matter of course that Crown Commissioners 

 recommend the em]>loyment of the government Caleb Quotem, 

 " the Corps of Royal Engineers," to execute a survey of the metro- 

 politan districts. This we conceive to be the finishing touch to 

 the wrongs and insults which the Sanitary Commissioners have in 

 this Report, and in their proceedings, heaped up'on highly honour- 

 able professions. 



If it be needful to show that engineers, architects, and surveyors 

 can be of some use, we shall appeal to the Report of the Sanitary 

 Commissioners, the recommendations in which are based on' the 

 evidence of Mr. Roe, the Surveyor of the Holborn and Finsbury 

 District, Mr. Phillips, the Surveyor of the Westminster District, 

 and other aide officers. In truth, as our pages would show, Mr. 

 Roe has, by liis indefatigable exertions, already carried out mucli 

 of the plans now advocated by the Sanitary Commissioners, and 

 has only been prevented by the Commissioners of Sewers from 

 doing more. Surely these officers are to be balanced against those 

 who liave adhered to a practice which has only recently been 

 opposed and condemned. AVhat do the commissioners tell us.-* 



" All the improvements which the public have yet obtained in 

 this branch of public works, have been the result of the special 

 and undivided practical attentions of well-qualified paid officers, 

 and it appears to us that furtlier improvement must be sought by 

 the same means, and that one of the chief objects of future ad- 

 I ministrative arrangements must lie to secure, ))rotect, and encou- 

 j rage the zealous, undivided attention and efficient labour of such 

 officers." 



If engineers and surveyors have already effected " all the im- 

 provements wliich the public have yet obtained in this branch of 

 public works;" and if to them, as scientific officers, the public have 

 to look for future im)irovements, we can see no reason for the slur 

 cast on them by their exclusion from the present commission, by 

 the announced exclusion from future commissions, and by the em- 

 ployment of the Corps of Royal Engineers, of whom — with all re- 

 spect be it said — the reputation is not European. M^e cannot hold 

 the appointment of Mr. Austin to the secretaryship of the com- 

 mission, nor the compliment paid to the executive officers of the 

 Commissioners of Sewers as any alleviation of the intended slight. 

 We hope Mr. Edwin Chadwick, as commissioner, and Mr. Austin, 

 as secretary, both of whom have done well in the cause of sanitary 

 reform, have had no part in the exclusive policy of the com- 

 mission. 



We have the highest regard for the medical profession ; we have 

 the strongest feeling of the good it has done in promoting sanitary 

 reform ; but we cannot stand still while medical men arrrgate to 

 themselves the merits, the honours, and the rewards of sanitary 

 reform. Their agitation has done good, we admit ; their disin- 

 terested advocacy of the cause claims the highest praise ; their 

 evidence has given a body and strength to the movement ; but it 

 is our professions which have worked while theirs have talked, — 

 which have improved the forms of the sewers, and reduced the price 

 — wliich have cleansed them by flushing, and which by a mass of 

 individual labour have perfected and carried out plans of improve- 



