196 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[JUNJE, 



poilant of liw^p arc the street lamps. These m:iy either be arranged 

 at considerable distances, and l)e titled with powerful burners, or the 

 intervals between them may be smaller, and only a single jet be al- 

 lowed fur each. Various local considerations must determine this, as 

 well as some other jioints: but it should be kept in uii- d, that the 

 best small light is either the single jet of three inches and a half or 

 four inches high, or the iish-lail jet of three inches high, and that for 

 more powerful lights l!ic argand is preferable to all ctJurs. The large 

 bat-wing, so much used in large public lamps, is wasteful, smokes the 

 lantern, and does not give light in proportion to its expenditure. 



In most towns, framed square lanterns are used for street lamps, as 

 it is said that globes are apt to be obscured in cold weather by the 

 deposition of the water generated by the combustion of the gas. It is 

 no doubt true, that if proper precautions be not taken, this inconve- 

 nience would be felt, and the water which would trickle from the 

 aperture in the bottom of the globe would be liable to freeze in severe 

 weather, and so to close up the access fur air, that the lamp would 

 smoke or go out. In all other respects, globes have undeniable ad- 

 vantages over framed lanterns, as they protect the flames better in 

 high winds, and they are ke|it up at much less expense. 



Some years ago I pointed out to the commissioners of police of this 

 city, that advantage might be taken of the acknowledged good pro- 

 perties of the globes for lighting the streets, and the alleged defect be 

 obviated bv constructing the tin tops with chimneys which should 

 reach '!own to the points of the flames, and by their current carry off" 

 the water while still in a state of vapour, and so prevent it from being 

 condensed on the sides of the globes. This plan was immediately 

 tried, and having been found successful, was adopted in all the lamps 

 erected subsequently. It occasionally happens, that from the jet 

 being deranged, the gas is directed past the tin chimney instead of 

 into it, and if the weather be cold, it is immediately observed that a 

 deposition of water takes place inside the globe, and its sides become 

 dim. The adjustment of the burner restores the proper action, and 

 the globe remains bright. This plan having now stood the test of 

 many years experience, may safely be recommended for adoption 

 wherever new street lamps are erected. 



ON SETTING OUT RAILWAYS ON SIDELONG GROUND. 



Fig. 1— Sidelong Ground. 



Balance Line. 

 30.0 > 



C, centre line. G, surfece of ground. 



Fig. 2. 



R for the rate of inclination of slopes to a 15 feet length, H for height 

 of balance line below or above surface at centre stake, h for difference 

 of level between ground at centre peg, and at 1,5 feet on either side 

 horizontal distance, and .c for the actual height above or below balance 

 line, at which the slopes run out to the surface. 



We have ^ x -\-n -{-h — xoT(li + h)R — Rz — rxoTthe lieight 



above the balance line, at which the slope cuts out on the higher side. 



Halance Line. 



Sir — Should the following formulae for setting out widths of railway 

 land OB sidelong ground be new, and in your opinion worth insertion, 

 please to give them a place in your next number. 



Suppose the centre line of way staked out and pegs driven into the 

 ground at every chain's length, an<i further that levels have been taken 

 at each of these lengths, both at the pegs and (in the case of a 30 feet 

 base) at l.") feet horizontal distance on each side. 



Then putting r for the rate of inclination of ground to a 1.5 feet length, 



R 



.r-t-A-l-3:=rHorHR — iR = r3--l-Rr, orthe height above 



the balance line, at which the slope cuts out on the lower side. — 2. 



For example, in the case of a 2U feet cutting with base 30 feet, 

 slopes IJ to 1, and the surface of the ground varying in level from 

 3-9 feet above the centre peg,- at 15 feet on one side to 3-9 feet be- 

 low at the same distance on the other side. 



By formula 1, (20 -f 3-9) 10= 10 a: — 3-9 .r. 

 239-0= t;-l.r. 

 39-2 =r X at li 1 = r.'^S, + 15 := 73-8. 



73-S horizontal distance to be set off' from centre stake on higher 

 side. 



Again, by No. 



-3-9X 10= 3-9 .r+ 10 .r. 

 = 13-9 X. 



= X. 

 horizontal distance 



to be set oB 



20X10- 



un- 



11-5 



At LHo 1 = 17-2 + 1.5 = 32-2.5 

 from centre stake on lower side. 



It is here understood that these calculations are made in the evening 

 after return from levelling, the depths of cuttings or embankments ob- 

 tained by reference to a section run before hand over the centre line of 

 way, and that the results of widths are pegged out on the following 

 rooming. 



Another example is here added, in which the ground is shown as 

 very irregular, although few instances occur to such an extent unless 

 perhaps in Cornwall, &:c. The depth of cutting and slopes with base 

 same as before ; levels supposed to he taken at A B C D on one side, 

 and at E and F on the other. The extent of levels necessary roust be 

 left to the judgment of the party acting. 



B 2-7 E= 8- 



C4- F=15- 



■ D 5-5 



12-2 levels above A. 23- levels below A. 



It is clear that in order to eq\ialize the inclination of the surface, we 

 roust obtain a figure forming an arithmetical progression, in three 

 terms to the amount of the higher side levels, but in two terms only to 

 that of the lower. 



Take 12-2 as before, of which 2-04 is the number required for the 

 higher side inclination, and 23 of which 7-7 is the figure for the lower. 

 Then according to our previous formula — 

 1. (20 -i- 2-04.) 10 = 10 a: — 2-04 jr. 

 220-4 = 7-9t; X. 

 27-69 = .r at U to 1 — 41-53 -f 15= 50--.53. 

 56-!53 to be set off" as the horizontal distance from centre peg op 

 higher side, correct -9 of a foot. 



Again No. 2. 'iOx 10 — 7-7 x 10 = 7-7 :;: -f 10 x. 

 123- = 17-7 X. 



(;-93 =jrat li to 1= lu-42, + 15. 



=r 25-42 to be set off' as the horizontal distance from centre peg for 

 lower side. 



I remain, your obedient servant, 



Geo. B. W. Jackson. 

 Raddifft Terrace, Gosrreli Roeid, 

 April 27, 1S41. 



* The centre peg in Ibis case supposed to be level with ground. 



Slon,' Cutting Mnch inc. —The .Alsace (.Strazburg) stales Ui.il a iialive of that 

 town, named Mullcr, has invented a simple and ilie.ap machine, set in motion 

 by the force of a single dog, turning like a horse in a mill, whereby a stone 

 in its roughest state is in five minutes cut into a rep-ular shape fit lor build- 

 ing, and its faces have an unusnal smoolline.ss. This machine is capable of 

 working twelve stones in an hour, or 144 in a day of twelve hours, being 

 c(iual to the labour of forty men employed for the same lime. Muller (adds 

 the journal) possesses several quarriesof stone, boih hard and soft, and works 

 his mill daily in the presence of numerous spectators. 



