1843.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



87 



Let 2'= temperature to which the steam is raised out of contact with 

 water, 

 s =: mean specific heat of the steam between the temperatures 



212° and*'. 

 D = the volume of steam at the temperature I' — the volume at 



212° being 100. 

 x — the volume of the same w : eight of steam at 32', supposing 



that it could be cooled to 32° without condensing. 

 A — heat required to raise 100 volumes of steam from 212° to V 

 5=r weight of water in 100 volumes af steam at 212°. 

 c = heat required to raise the temperature of a quantity of water 



= b 1°. 

 A' = heat required to generate from water at 60° a quantity of 

 steam equal in volume to v — 100. 



From (1) we have af + * X *btt (212 — 32) = 100 or (since T i 7 y = 

 •002083) x + x X -0020S3 x 180 = 100 : ■ x (1 + -37494) = 100 



100 

 0r X = 73749? 



From (1) also we get v = 100 + x X -002083 (l' — 212) which by 

 substituting the value of x previously found becomes u = 100 -j- 

 •2083 (f — 212) 

 1-37494 

 From (2) we find 100 : e : : -S47 : specific heat at the tempera- 



*8470 

 ture V which is therefore — — - hence 



s = j ( — — — \- -847 \ or by substituting the value of r. 



000S82 (V — 212) 



F37494 

 - 212) s c, which by substituting the value of s 



S47 + 



But A = (l' 

 becomes 



A = { -847 (*' — 212) + 



000882 (T — 212) - > 



7 



•137494 



Now the addition to the volume of steam produced by heating it from 



212° to i' = v — 100 = 



•2083 (t'~ 212) 



and the water in an equal 



1-37494 

 volume, may be found by this proportion 



•2083 (i< — 212) , -002083 (i 1 — 212) 6 



100 



1-37494 



1-37494 



= weight of water in a quantity of steam, whose volume at 212 is 

 o — 100. Hence, supposing the latent heat of steam to be 1000° we 

 have 



,/«« . ,™« -002083 (i' — 212) 2-3954 (T — 212) 

 A = (1000 + 150) „ X j^j = j^gj C 



Now since A z= heat required to produce an additional volume of 

 steam equal to v — 100 by heating the steam out of contact with 

 water, and since A' — the heat required to make the same addition to 

 the volume of the steam by generating it from water, it follows that 

 the saving of heat by using the former method is h' — A 

 _ 2-3954 (<' — 212)e f g, 7 „, _ ai» J. 000S82 (f 212) * ) 

 1-37494 I " V 1-37494 i 



which reduced = 



1-37494 

 1-230S (f — 212) — O00SS2 (f — 212) 2 c. 



1-37494 



The weight of water in steam equal in volume to v at 212° is evi- 

 dently b — consequently the heat required to generate from water 



steam equal in volume to v, is 6 -j—tl " — r — which by substituting 

 •00283 (? — 212) 



the value of b becomes 1150 



/, -00283 (/ — 212) \ 

 \} + F3T491 ) 



And this being reduced gives the whole heat required to raise steam 

 equal in volume to » from water 



_ 1581- 181 + 2-3954 (f — 212) 



~~ 1.37494 C 



consequently by this formula the 

 the whole heat used in generating 



*'-*- K371 ' 11 



heat saved is expressed in parts of 

 steam in the usual way 



1581- 181 + 2-3954 (f —"212) ' c by substituti "g *tabe- 

 1-2308 (f — 212) —000882 (f — 212) ' 



1581- 181 x 2 

 If the steam be heated to 600° 

 such case gives the saving equal 

 Our former mode of determinat 

 nearly. The minute difference 

 been in the one case supposed to 

 inversely as the specific gravity. 



•3954 (f — 212) 

 then I' = G00 J , and the formula in 

 to about j-th of the whole fuel used, 

 ion gave the saving at B .y, or | very 

 arises from the specific he.it having 

 be uniform, and in the other to vary 



SEWERS OF THE METROPOLIS. 



To the Wonhijgful Her Majesty's Justices and Commissioners of Sewers 

 for Holbvm and Finsbunj Divisions. 



[In the last month's Journal we offered some observations on the 

 construction of sewers, and reserved the examination of other por- 

 tions of Mr. Donaldson's address and Mr. Chadwick's report for 

 another occasion. Since writing those observations, we have had put 

 into our hands a very able report drawn up by Mr. Roe, the surveyor 

 to the Holborn and Finsbury divisions of sewers. As this report so 

 fully enters into the subject of "flushing," we abstain from offering 

 any remarks of our own, but leave it in the hands of Mr. Roe, whose 

 experience on the subject, enables him to report upon it far better than 

 we could have done had we attempted it: by a reference to the en- 

 graving of Mr. Roe's flushing apparatus, given in the last September 

 number of the Journal, Mr. Roe's report will be better understood, 

 and to all those of our professional readers who may take a deep in- 

 terest in the question, we strongly recommend them to inspect the 

 apparatus fixed in the sewer of Hatton Garden, opposite the office of 

 the Commissioners of Sewers of the Holborn and Finsbury divisions, 

 by an application to the Clerk of the Commissioners, we feel assured 

 that any member of the profession will meet with the same courtesy 

 that we did, and obtain permission to inspect the apparatus. 



At the Court, held October, 1842, an order was made " that the surveyor 

 prepare and lay before the next court, a Report as to the result of the use of 

 flushing apparatus for cleansing sewers, with an account of the expense in- 

 curred, and probable saving to the Commission, and embracing the general 

 improvements in drainage that have been adopted by this Commission." The 

 surveyor, in obedience to that order, has prepared a report, winch he begs 

 respectfully to lay before you. 



Several honourable Commissioners at the last court having expressed a de- 

 sire that the surveyor should give as full explanation as possible of the me- 

 thod of flushing, and as to what effect it would have upon sewers having 

 little or no fall in them, and upon private drains, it seems necessary to enter 

 into some detail of the cause of flushing being suggested from the necessity 

 that exists for using some artificial method to clear large portions of the 

 sewers from the foul deposit that accumulates in them. 



The Holborn and Finsbury divisions are peculiarly situate as bavin;; no 

 immediate connexion with the River Thames as an outlet, the waters from 

 these divisions having to pass through one or other of the adjoining districts 

 of the city, the Tower Hamlets or "Westminster, Lefore reaching the river. 

 The sewage of the Holborn and Finsbury divisions has therefore of necessity 

 been formed to such outlets as the other districts presented for usi 

 these formerly being put in without a due regard to an exten le I drainage, 

 the sewers of your Commission have not had the benefit of the best fall that 

 could have been afforded to them. Of late years, the adjoining districts 

 have lowered many of their outlets ; but to alter the existing sewers of your 

 Commission to the amended level, would require the rebuilding of about 

 323.706 feet of sewer, at an expense of about i'200,000, exclusive of the cost 

 of connecting sewers where the rutting would be deep, and of con: 

 existing surface and house drainage with them, which would make the total 

 amount of cost nearly a quarter of a million. S ill, aa the lowering of those 

 outlets has taken place, you have availed yourselves of them to a considerable 

 extent ; witness the line of sewer to Holl way, the City Road line, th 

 well-street and Ooldcn-lane lines, and several others, varying in length from 

 one lo four miles. 



The city, some time since, sent to ask you, as data for the improvement ol 

 their sewage, the depth of sewage which it would Le desirable ultimately to 



12 



