18 



THE CIYIL ENGINEER AND AUCHITECT'S JOURNAL. 



It now only remains to notice the quality of (he iron. In no one 

 respect is it inferior to '' best common," and in many of its properties 

 it is eqnal to Swedish or charcoal iron ; its tenacity is so groat, that 

 of four trials made with patent iron (I inch chain), at the corporation 

 testing machine, Liverpool, not one broke with a less strain than 2fi 

 tons, and one link required 28 tons 12 j cwt. to break il, the standard 

 test for that size being 16 tons. 



Experiment on Mr. Clay's method of making bar iron. — ISOlbs. 

 of Ulverstone ore and 40jlbs. of wet coke (losing 12J per cent, in 

 drying) were put into one of the gas retorts in Dale-street, on 

 Saturday, Nov. 24, at five in the morning, and remained in till fen on 

 Tuesday evening, or sixty-five hours. The heat was maintained at a 

 full red, or common gas-making heat. The above quantity reduced 

 at the Mersey forge (two miles distant) produced in thirty-four 

 minutes two balls of iron — one of 321bs., and one of 261bs. — '581bs. 

 The former rolled to l-l inch puddled bar, weighed 301bs., and was 

 then brought down under the tilt to j inch square, and samples taken 

 when broken. The yield 38| per cent. 



Comparative result of melting iron in a cupola with a mixture of 

 antlu'acite coal and coke, and with coke alone, obtained from re- 

 peated trials : — 



Old method of filling and tuorking the 

 cupola with coke alone. 



Charge with coke 

 Ditto limestone . 

 Ditto iron 

 Ditto coke . . 

 Ditto iron . . 



And continue filling jcwt. 201b. 

 of coke to every 3J cwt. of iron, as 

 long: as necessary. 



New method of filling and working the 

 cupola, with a mixture of coke and 

 anthracite j'aw coal. 



The cost of coke fuel for melting each ton of iron, reckoning the 

 coke at 30s. per ton, is 3s. 8d. The cost of the mixed fuel, reckoning 

 the coke at 30s. per ton, and the anthracite coal at 25s. per ton, 

 is only Is. 8d. per ton, causing a saving of upwards of 50 per 

 cent. ; and the anthracite coal being almost pure carbon, has the 

 further effect of improving the quality of the iron. 



This experiment was tried at Messrs. Weber's foundry, Liverpool. 

 The anthi-acite coal was obtained from the Ystalyfera Iron Works, 

 near Swansea, now erecting under the direction of Mr. E. O. Manby, 

 civil engineer. 



N.B. The cupola which is now at work, according to the improved 

 method above described, is 2 feet 2 inches wide inside, 8 feet high, 

 and is blown by a fan blast through a twyere 6 J inches in diameter. 

 The blast was not heated. The quality of the iron was decidedly 

 improved by remelting with anthracite. 



FURTHER REMARKS ON THE SLOPES OF EXCA- 

 VATIONS AND EMBANKMENTS ON SIDELONCx 

 GROUND. 



Sib, — Having carefully read Mr. Bowman's contribution to your 

 number for tliis month, on the above subject, I am induced again to 

 address you. Mr. Bowman having stated the method he has described 

 as being more expeditious and more accurate than that described 

 by me iu your Journal for November, in reply to his statement, that it 

 is more expeditious, it could only have arisen from Mr. Bowman's not 

 having practised the method I described ; as instead of planting the 

 instrument at each estimated width from the centre, as iu tlie metliod 

 described by him, I set up the spirit level in such a position as to com- 

 mand the ground backwards and forwards for several hundred feet, in 

 which distance there would necessarily be several widths to set out ; 

 but this can be done only on moderately hilly ground. The metliod I 

 adopt, where the ground is very abrupt and sidelong, is to plant my level 

 so as to command the centre stakes, and as many of the upper widths as 

 possible, which I rectify in the manner I have previously described ; 

 I then remove my instrument so as to command the centres and .is 

 many of the lower widths as possible, which I alter in a similar manner ; 

 in this way the widths on sloping ground, however rapid the fall may 

 be, can be set out with great facility. 



It must be very apparent to your readers that once planting liie spirit 

 level can be done much more expeditiously tlian(I speak within compass) 

 half a dozen times wif ': tlm tbporlolite — not taking into account tlie much 

 longer time requisite in planting th« latter instrument than the former. 



As to the greater accuracy, if Mr. Bowman does not impugn the method 

 I think there is no doubt but that with the spirit level is infinitely 

 superior, bearing in mind that the calculations with the latter in the 

 field (simple as they are) is not trusted to the head only, but the read- 

 ings of the staff', registered (on a waste sheet), and the necessary deduc- 

 tions or additions made ; but without this latter precaution I cannot 

 understand why a mistake wo\ild be less likely to occur in first reading 

 the level staff, then setting the instrument to the angle of the slope and 

 again reading the staff, than it would be to simply note the diff'erence 

 of level, multiply it by the slope, and correct the distance accordingly. 

 In conclusion, although I would be sorry to be thought discourteous 

 towards Mr. Bowman, whose method I highly appreciate, and in some 

 localities would undoubtedly practise it, yet I much doubt its useful 

 application in the majority of instances. 



I remain, &e., 

 Charlotte-street, Bloomsburv, PETER BRUFF. 



Decembej-, 1838. 



MOMENTUM OF FALLING BODIES. ' 



Sin, — Oblige me by allowing your Journal to be my medium for 

 submitting the following remarks to the perusal of your correspondent 

 C. E. C, and your other, I hope, numerous readers. 



Mathematical works tell us that the momentum of a body in motion 

 is proportional to its weight multiplied by its velocity. I doubt this, 

 and the following is my reason for so extraordinary a scepticism : — 



The velocity of a body at rest (or, to avoid a contradiction, of a 



body all but at rest) is evidently z= x^^^^i^. = 0. If tn were as 6 v, 

 the force or pressure of a body just moving from a state of rest would 

 be ; for. as we have already seen, v then = 0, and 6X0 = 0, 

 whereas in fact it is b. 



I beheve that the momentum of a body can never be less than its 

 mass, and that it is equal to the body's mass added to the product of a 



certain function of the body multiplied by the velocity — or, algebrai- 

 cally expressed, that m =: b -\- M *''. 



I have some years ago endeavoured to measure the ratio of the 

 momentum to the velocity per second of time. I repeated an experi- 

 ment after reading your correspondent C. E. C.'s letter, and the 

 following is an account of it and the results I deduce from it : — 



Having- attached one end of a cord to a weight of half-a-pound, I 

 tied the other end to the hook of an accurate improved spring balance, 

 by Salter, and having made the distances from the hook to the weight 

 successively 16 feet, 8 feet, 4 feet, 3 feet, 2 feet, and 1 foot, let the 

 weight fall these distances, and observed that the scale marked nearly 

 241bs, lOlbs, 14ibs, 121bs, lOlbs, and 6Jlbs, so that the power acquired in 

 falling the distances was for a velocity of 32 feet per second = 23ilbs ; 

 fur22| feet= 18^; for IG feet = 13^; for 13;; feet = 11^; for Hi 

 feet = 9^ ; and for a velocity of 8 feet per second =: 61bs. Dividing 

 the velocities by the weights, we find that a body falling (or a body in 

 motion) at the rate of one foot per second acquires a force equal to 

 10-7ths and 13-8ths of its mass, or, perhaps, very nearly once and a 

 half its mass or weight. The momentum, then, is equal to the sum of 

 t he weight and the product of the weight multiplied by once and a half 



the velocity per second, or wi =: 6 -j 2" ^= 1* "I" "0-1/32 s, where s 



= the space fallen through. 



A monkey of 2001bs. weight falling 25 feet on a pile head will, 

 therefore, strike it with a force equal to the weight of 200lbs. -j- 



'—j^t/SOO = 8,685lbs. nearly ; and a weight of lOJ.OOOlbs. falling 

 one-hundredth of a foot would strike with a force equal to a pressure 

 of 100,OOOlbs.-}-^552^|^ 1/0^01X^32 = 184,840ibs.: or it will 

 require a force of 184,840lbs. to lift 100,0001bs. one-hundredth of a 

 foot, with the velocity of fifty-six-hundredths of a foot in a second. 

 By the old formula of m — hi\ which has been erroneously applied for 

 ?« is as bv, this weight would be moved at the above rate by a dead 

 weiglit of 5(),0001bs, 44,0001bs. less than its weight. 



I remain, yours obediently, B. 



COL. C. W. PASLEY, C.B., F.R.S., &c., AND MR. GEORGE 

 GODWIN, JUN., F.S.A. 



[We have been requested to insert the following letter, addressed 

 to Col. Pasley, in reference to the di.'-puted point touching the first 

 use of concrete in England.] 



Sir, — I'crniil me, although personally a stranger, to claim your 

 attention for a few minutes. 



