1844.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



JOS 



Table of the comparative evaporating power of t\iree different 

 methods of tubing: — 



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It appears from the above, that the boiler which is tubed in the 

 theoretic proportion is from 12 to 20 per cent, superior to tlie others. 



Let us now determine the area of the tubes, as cojnpared with the 

 whole space, when the preceding theoretic ratio is adopted. 



= the number of tubes in one horizontal row A B. 



the vertical distance between the horizontal row s 



4c 

 4 c V' =2c v/3 



:= the number of horizontal rows in A D. 

 6 — c (a — c) (b — c) 



8c= V3 

 Diameter of a tube =: 3 c 



the wliole number of tubes. 



Oir 



(a-c)(6 — e) = 



Sc'l/S ^ 32V3 



the area of the tubes : from which it may be observed that tlie diameter 

 of the tubes disappears from the expression, indicating that so long as 

 the ratio between the diameter and interval remains the same, the 

 aggregate area will be constant, let the actual diameter be wliat it 

 . 9 ir 



may : and the value of ^^ = 0'51. The area of the tubes will. 



32v/3 ' 



therefore rather exceed the half of the space. 

 Manchester. Geo. W. Buck. 



o A 



ENTASIS OF CHURCH SPIRES. 



Sir — In a report of a recent meet- 

 ing of the Royal Institute of British 

 Architects, given in your journal of 

 Jan. 27, 1 observed some remarks up- 

 on the question of entasis in spires, 

 from which it appears, that the 

 gentlemen who took part in the 

 discussion had not recognised de- 

 cided curved lines in any spire ex- 

 cept that of Newark ; 1 am happy 

 to be able to instance, from the same 

 district, a much finer and better 

 developed example than the spire 

 of that church, which, it is true, 

 has a positive though slight entasis: 

 the accompanying drawing, should 

 you think it worthy of a place in 

 your valuable Journal, and which 

 is an elevation of the steeple of 

 Gedling Church about four miles 

 from Nottingham, will more clearly 

 exemplify this assertion : the scale 

 and measurements may be depended 

 upon, as the latter were taken 

 during some repairs at the summit 

 of the spue. It will be perceived 

 from this that the amount of varia- 

 tion or bulging from a straight line 

 drawn from the base to the summit, 

 is very considerable, being in the 

 widest part not less than two feet; 

 indeed tlie swell is so great as to 

 prevent a person, standing upon 

 the leads of the tower, seeing the 

 weathercock, unless by leaning over 

 the battlement: the curve extends 

 43 ft. from the top of the battle- 

 ment, where it meets the straight 

 lines of the rest of the spire, and 

 forms a segment of a circle whose 

 radius is about 27Uft. 



The style of the spire is of what 

 I should denominate the second 

 decorated; circa 1320: and it is, 

 perhaps, worthy of remark, that 

 Newark is also of decorated date, 

 although somewhat later than Ged- 

 ling. It is situated at the north 

 west angle of the nave; and conse- 

 quently groups very picturesquely 

 with the body of the church, which 

 possesses many interesting features, 

 and has a most exquisite early 

 English chancel of rather unusual 

 dinieiisions (50 ft. by 24ft.): there 

 are I'unr uiclies occupying llie alter- 

 nate faces of tlie spire as iu;licatcd 

 in the drawii g; they coiiiain male 



jj» 



