178 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



I June, 



that tlie freshets should, if the water could be spared, be prevented 

 friiin I'titerins tlie reservoirs. 



Under tlicir act of iiarli.-iinent the corporation are to take all the 

 water of Lonfrdendrile into their reservoirs, and supply a daily 

 quantity to the millowners. This, Mr. Ilomershain affirms, will 

 cauae a greater expense for reservoirs, and will yield less water to 

 the corp(u-ation ; and he contrasts it w ith tlie system adopted on the 

 Peak Forest Canal, where all the water above a certain gauge goes 

 into the canal reservoirs. 



When he says that reservoirs for the millowners have not an- 

 swered (p. 44.), and that therefore money is not laid (uit liy the 

 millowners in that way, leaving the inference that the corpcn-ation 

 reservoirs will be fouinl exjiensive and useless, we think he strains 

 his case too much, for there arc many difficulties in the case of 

 millowners, as that of getting all the millow ners and landowners on 

 the stream to join, and the great expense of getting an act of par- 

 liament. 



We must notice that there is a great deal of valuable matter in- 

 cidental to the discussion of the several schemes, which may be 

 usefully read by the engineer feeling an interest in this im])ortant 

 branch of practice. Thus, Mr. Ilomersham dis<-usses rain-gauges, 

 the fall of rain, the duration of fall, evaporation, absorption, and 

 nitration. We should like to see complete records of the move- 

 ment of some considerable streams. Mr. Ilomersham says below 

 tJiat he has made such, and we wish he had published them. 



" The quantity of water flowing down streams fed from rain falling on 

 the sides of hills varies with every |tHS>iiig .shower; no one or two observa- 

 tions per day can possibly give anythiny tike an accurate result ; a flood will 

 somelinies last but a few liours, and yet in this time it frequently happens 

 more water will run down the streams than at other times will flow down 

 in as many weeks. I have iiad occasion to make observations on streams 

 every hour in fine weather, and every half hour in showery weatlier for 

 weeks together, day and night, and iu unsettled states of the weather 

 almost every measurement varied." 



Mr. Ilomersham gives an estimate of the cost of the corporation 

 works, which at five per cent, makes a yearly cost of 20,835/., while 

 he asserts that the same quantity of water, of better quality, can 

 he had of the Manchester, Sheffield, and Lincoln Railway Company 

 for 13,968/. \5s. yearly, being a saving of nearly 25 per cent. All 

 this, however, depends on what the real cost of the corporation 

 works may be, and for that purpose we should have the estimate 

 of their engineer, and not of Mr. Ilomersham. Indeed, the whole 

 gist of the question lies upon this, which must likewise be the 

 comment on his concluding statement. 



" As you are aware, iu the spring of last year the corporation could 

 have made arrangements to secure for the use of the inhabitants of Man- 

 chester, eight millions of gallons of filtered water per day (as much as will 

 be required for the domestic use of the borough for some years to come), 

 delivered at INIarple, 320 feet above the high part of the town, for l^d. per 

 1,000 gallons : in August last year (after having spent a large sum of money 

 in opposing your scheme), the corporation, in conjunction with the Water- 

 works Company, purchased of you, fur three years certain, two hundred 

 millions of g-allons per annum of the same water tmfillered, to be delivered 

 ID the Gorton reservoirs, at 3d. per thousand gallons ; or at double the 

 price they might, by adopting a wiser course, a short time previously have 

 secured the same viMer jfiltered." 



EXPLOSIONS OF STEAM-BOILERS. 



TheCmisex ntid Efl'i'ctx ofE.rpJnshms in Steam-Eiijiines Inrestiynted ; 

 and their result frinn on explonire jiriiiciple different from tlie force of 

 ejaxtic steam demnnstriited ; and citnelusiee eridenee adduced that more 

 titan four-fifths of the veiijht and strength of the engine are required to 

 xustaiit the e.rpliisire force : u-ith an easy and certain means of prevent- 

 ing its destruetire effects., and reilncing in great part the enormous 

 weight of the engine. By John Wiminit, New York. 1847. 



The elaborate title of this pamphlet fully explains the views and 

 objects of the writer, who lives in the land of steam-boiler explo- 

 sions, and seems to have had much experience therein. He com- 

 mences by adducing a number of facts which are valuable in their 

 way, but his inferences from them seem inccuiclusive, ;ind often 

 very fallacious. After mentioning several instances of the ex- 

 plosion of cylindrical boilers, in which the ends were blown off and 

 projected to great distances, he proceeds to make calculations of 

 the strength of the relative parts of such boilers, and concludes, 

 that " it is im])ossible that a cylindrical boiler should be rent 

 asunder endwise by the force of elastic steam, since half the force 

 requisite thereto would hurst it ojien laterally." The following is 

 a specimen of the calculations on which he found this assumption : 



" The diameter of the boiler which exploded at Balfiuore, is stated iu the 



Sun at 20 inches; the circumference, therefore, C2'82 inches, one-fourth 

 whereof, 15-705, multiplied by 20, tlje diameter, gives 3141 square inches 

 as the area of the end of the boiler ; but the whole periphery or ring resists 

 the pressure on the ends, and ita cohesive strength is the circumference, 

 62'82 inches. In like manner the rectangular section of the boiler, niaiie 

 by a plane passing through a portion of the axis nne-fcmrth of the circum- 

 ference in length, is 15*705, nuiltiplied by 20, the diameter, is equal to 

 314'1 square inches, the area ; and the pressure perpenilicular thereto, the 

 effect whereof is to burst open the boiler laterally, is resisted hy the cohesive 

 strength of half the circumference, 31-41, or the two portions of the ring or 

 periphery, each 15'7fl.'> inches long : wherefore, in all cylindrical boilers, the 

 amount of metal which resists the pressure on the ends is double the amount 

 of metal which resists an equal lateral pressure ; and it appears impossible 

 that they should be rent asunder endwise by the force of elastic steam, 

 which can never exceed the strength of the boiler in which it is generated. 

 The area of a circle is greatest in respect of its periphery, of any figure what- 

 ever ; much less, therefore, can a boiler not cylindrical be rent asunder end- 

 wise hy the force of steam. But numerous cases have occurred wherein 

 boilers have been rent asunder endwise, which could only be effected by an 

 almost unlimited explosive power. No trace of such power is found in the 

 history of boilers other than those of steam-engines ; nor in these has it been 

 indicated by the safety-valve or steam-gauge, although they show, with suffi- 

 cient precision, the variations in the strength of steam. Against the force 

 of elastic steam, as generated in a huilcr, a properly loaded safety-valve is a 

 complete security, hut it has not the least value as against the effects of ex- 

 plosive action." 



The " explosive principle," to the action of which Mr. Wilder 

 attriliutes most of the accidents in steam-engines, ap])ears to be 

 electricity, though it is not so stated distinctly. This force is, he 

 conceives, generated principally in the valve chambers in the fol- 

 lowing manner. 



" It has been proved (?) that explosions in steam-engines are the conse- 

 quence of the escape of elementary caloiic from its combination with water 

 or its vapour, and result directly from the removal, in the valve chamber of 

 engines, of the compressing force which kept up the combination ; for when 

 the steam-valve is opened, the steam which passes into the valve chamber 

 has free space to expand and the caloric to escape, but that escape and the 

 further opening of the valve must diminish in a degree the compressing 

 force, and be followed hy a farther escape of caloric ; but its amount and 

 consequent action must depend more or less on the temperature and ex- 

 pansive force of steam within the boiler. The occasional violence of its 

 action is shown by the prodigious strength of the beatus, cranks, &c., which 

 are soitietimes broken. It is apparant from all considrrations, that if the 

 valve chambers be disused, and the steam let directly through the ends of 

 the cylinder, the smallest clearance of the piston from the end, which does 

 not admit its touching, will be the only vacant space for expansion and 

 escape, and this need not be an hundredth part of the space in the valve 

 chamber, and of consequence the explosive action cannot exceed the hun- 

 dredth part of its present violence." 



Though Mr. AVilder considers he has " proved" his position as 

 to the cause of explosions in steam-engines, we confess that his 

 evidence is not sufficient to satisfy us; ami bis opinions are fre- 

 quently formed on erroneous data. He adduces, again and again, 

 as an illustration favourable to his theory, the explosion of a ^\in 

 barrel when merely corked at the muzzle, but he does not seem 

 fully to comiireheiid the cause of its exploding under such circum- 

 stances ; which the explosive force of gunpowder is sufficient to 

 account for, without the supposition that any new force is suddenly 

 brought into action. High-pressure steam is, according to Mr. 

 'Wiliier, " the most elastic, yielding, and manageable of all prime 

 movers," and only requires to be kept close, so as to prevent the 

 escape of the "elementary caloric," to become as inexplosive as 

 water power. We might hence indeed infer, though probably Mr. 

 ^V'ilder is not prepared to go so far, that high-pressure steam is 

 dangerous only when it escapes, and that what are usually con- 

 sidered safety-valves ought to be regarded as generators of explo- 

 sive force. 



Carbonic- Jcid-Cas Enyine. — Another attempt to apply carbonic acid gas 

 as a motive power, has been brought before the notice of the Paris 

 Academy of Sciences, by IM. .lagu, CI"-., who proves very satisfactorily the 

 gieat power tliat may be readily ;;aincd by imparting a comparatively low 

 temperature to carbtmic acid gas ; but ttie ddlicult problem of condensing 

 the gas, to render it again available, seems not to have been solved. M. 

 Jagu calculates that, by suitable apparatus placed at each station, six 

 atmospheres of carbonic acid gas may be compressed for an unlimited 

 time, fron) whence the receiver may be tilled. To make tlie gas re-enter 

 the condensing apparatus with the absorption of as little po\\er as possi- 

 ble, he proposes to place a lever on each side of the engine, put in motioo 

 by eccentrics adapted to the fiist moving wheels ; at each extremity of the 

 lever to be placed a. winch, which will move two pistons of a given 

 diameter, so that the gas may pass iu and out. 



