THE INJURIOUS EFFECT OF A BLUE HEAT ON STEEL AND IRON.* BY C. E. STROMEYER, Assoc. M. Inst. C.E. It was stated that, in spite of the many excellent qualities possessed by mild steel, and in spite of its extended use for shipbuilding and for marine boilers, many engineers considered it a treacherous material. They were able to adduce nu merous instances in which steel plates and bars had failed, in their opinion, in an unaccountable manner. In nearly all such cases a cursory examination brought out the fact that the plates in question had been subjected to bending or hammering while hot, and there could be little doubt that while they were being worked these plates were at a blue heat, or as smiths and boilermakers termed it, a black heat. It should by this time be well known that such treatment was the most injurious to which steel could possibly be subjected, and therefore such failures could not be properly regarded as unaccountable. Iron possessed the same peculiarity, but being less ductile than steel, similar failures were not so glaring The author then mentioned cases in which plates, both of iron and steel, had failed without this treatment, although the quality of the material was good, according to the usual tests. Three hundred and thirty experiments had been made in connection with the subject of the paper, and consisted mainly of bending and of tension tests. The results were contained in tables and in diagrams. It appeared that the limit of elasticity of both iron and steel was raised by repeated tension testing. In some cases the limit rose above the original breaking stress, although the ultimate breaking stress was only slightly affected. The total elongation was reduced by previous mechanical operations, while the contraction varied considerably. A test piece which had been shortened when cold showed a reduction of the elastic limit, but another piece which had been shortened when hot showed an increase. By the expression "blue heat" the author meant to include all those temperatures which produced discolorations (ranging from light straw to blue) of the surfaces of bright steel or of iron. The author showed that steel which had been bent cold, either once or twice, would stand almost as many subsequent bends as the original test pieces. But if the same material was bent once while blue-hot it lost a great deal of its ductility. Out of twelve samples, in which two preliminary hot bends were made, nine broke with a single blow of a hammer, and the other three only stood one or two subsequent bends. Thin Lowmoor iron did not break quite so easily, but supported about one-half the original number of bends. The following Table contained some of these results: A Paper read before the Institution of Civil Enginers on the 16th of January. INJURIOUS EFFECT OF A BLUE HEAT ON STEEL AND IRON. 371 The experiments all pointed unmistak- against such failures, and should be enably to the great danger incurred if iron couraged. It consisted in the cessation. or steel were worked at a blue heat. of work as soon as a plate, which had The difference between good iron and been red hot, became so cool that the mild steel seemed to be, that iron broke mark produced by rubbing a hammer more readily than steel while being bent; handle or other piece of wood over it, that iron suffered more permanent injury would not glow. A plate which was not than steel by cold working, but that if it hot enough to produce this effect, yet had successfully withstood bending when too hot to be touched by hand, was most hot, there was little probability of its probably blue-hot, and should under no flying to pieces when cold, like mild circumstances be hammered or bent. steel. It was a common practice amongst The theory, that local heating of a boilermakers to "take the chill out of a plate set up strains which sometimes plate" if it required a little settling, or caused failures, did not appear to be supto set a flanged plate before it was cold. ported by the experiments. But it was This was nothing else than working it doubtful whether the proposal to locally blue hot, and should not be allowed. All reheat a plate, which had been worked hammering or bending of iron and steel when hot, in order to anneal this part, should be avoided, unless they were should be carried out. Several test pieces either cold or red-hot. Where this was were made red-hot or blue-hot, and then impossible. and where the plate or bar were slowly cooled, by holding one of had not broken while blue-hot, it should their edges in cold water. As might be subsequently annealed. It was satis- have been expected, the medium hard factory to learn that, since the introduc- steel lost much of its ductility. The tion of mild steel, a practice had been other steels and the iron were not greatly gaining ground amongst boilermakers, affected, as would be seen from the fol which must have the effect of guarding lowing Table: The author concluded by suggesting | Bourdin, and published in La Lumière that the question should be further in- Electrique, Professor Clausius says, that vestigated, and that steel manufacturers the mean path of the molecules, multishould endeavor to ascertain whether every quality of steel was made permanently brittle by being worked at a blue heat, or whether this was independent of the various impurities contained in it; and also whether prolonged exposure to a blue heat could produce the same effect. In a letter in reply to an epistolary communication of certain arguments as to the dimensions and relative distances of molecules advanced by Mr. Jules plied by eight, is to their diameter as the total volume occupied by the gas is the volume occupied by the molecules; and that if the gas departs from the law of Boyle and Gay-Lussac, the departure is due to several causes, one of which is that the volume actually occupied by the molecules cannot be neglected as compared with the total volume of the gas. In order to explain the propagation of luminous waves across space, it is requisite to admit the existence of a matter susceptible of more subtle division than the ponderable gases. ABSTRACT OF THE REPORT OF A COMMISSION TO CONSIDER A GENERAL SYSTEM OF DRAINAGE FOR THE VALLEYS OF THE MYSTIC, BLACKSTONE AND CHARLES RIVERS. this apparent waste, yet a great preponderance of evidence has convinced the best modern authorities that the loss is not a real injury. Not that any one denies that human excrement is a good manure. SEWERAGE may be defined as the re- larger towns in the State. The Mystic moval of what is popularly called filth, and the Sudbury are turned through the by water. For the purposes of this re- city at the rate of thirty million gallons port it has been found convenient to a day. This enormous flood is used, and consider household sewage, and the turned to sewage in the using. It must pollution of bodies of water by manu- then be got rid of; but how? To anfactories, separately. Confining our-swer this question in each case is the selves, then, more particularly to domes- science of sewerage. The simple and tic sewerage, it шау be said to be largely obvious way is to let it run into the nearan outgrowth of the modern systems of est water. This is the practice of the water supply. So long as people live earliest time, and it is still admitted to thinly scattered over the country, no dif- be the best where it is entirely practificulty arises about the removal of the cable. For, earnest as has been the prooffensive refuse of living. It is suffi- test of many noted theorists against ciently solid to be retained in suitable temporary receptacles for a season, and readily taken away from time to time to land, where it is valuable as manure. As long as the natural supply of clean water sufficed for the community, so long Nor can we controvert the the simple natural channels of absorption chemist when he offers to prove that and diffusion were able to carry it away every ton of Boston sewage contains two when made dirty by use. Even after the cents' worth of fertilizing matter. Adinhabitants in towns became closely mitting it all, the difficulty of extracting packed together, the same methods could it remains. Practically, no one would be made to answer by enlarging the take the sewage of Boston as a gift, alvaults into cesspools. It is still retained though in theory it may be a mine of in many large places, but it requires wealth. The truth is, that the excreata great care in management, and consider- and other valuable ingredients are so able expense to prevent nuisance. Speak- mixed with heterogeneous and often ining generally it is found easiest and jurious matters, so altered by chemical cheapest to use water as a vehicle for changes and so drowned in water, that entire removal. Especially is this ac- that they are of little or no value. It cepted as almost inevitable when the use costs more to get them out than they of water becomes as lavish as it gener- are worth when saved. Taking all the ally does in our towns when once a pub-accessible evidence into account, the very lic water supply is introduced. System- able and distinguished royal commission atic water supply turns "night soil" which lately discussed the whole quesinto mere dirty water, which can hardly tion of sewage disposal in connection be carried away in carts, or permitted to leach away through the ground. It calls for a channel of discharge as swift and capacious as its source of supply. Sewerage works are, so to speak, the corollary of waterworks, and, in our opinion, should immediately follow their adoption everywhere. Take the city of Boston for an example, on a large scale, of what is done in miniature in half the with the great problem of the London sewage, came at last to the conclusion that "in some very favorable cases a profit may be made without purification, and very frequently the purification may be made without profit; but the two cannot apparently be combined." Still, though it may be true that the simplest and easiest may yet be the best way of getting rid of sewage, it is not always suitable or safe. For, though diluted so much as to be valueless, it is not diluted enough to be harmless. It retains a facility for decay which makes it an offensive and a dangerous neighbor, and that, too, whether we cast it into the sea, or into estuaries or rivers or brooks. The defilement is often such as to cause alarming mischief. It may answer very well for New York to discharge her sewers directly into the Hudson and East River on either hand, or for St. Louis to drain straight down into the Mississippi at her feet, or for Chicago to lead her sewers into the lake under her very nose, but Boston found that it would not do to use her harbor, spacious as it is, for a cesspool; and London, after having spent twenty millions to empty her sewers ten miles below her on the Thames, now finds even that remote outlet so intolerably offensive that it must either be pushed on to the open sea, or some means of purification before discharge must be resorted to. Nevertheless, if it can be done effectually and finally, it is undoubtedly cheapest and best to cast the foul water entirely away into a body of clean water so large and so free that all trace of the contamination speedily disappears. But when the situation does not admit of this disposition-and this condition may result from a lack of a good outlet, as well as from mere distance from the water itself—we are brought to the discussion of the other systems of disposal of sewage which have obtained the greatest degree of acceptance among professional experts and practical engi neers. First among these are two plans for using earth in much the same way as we have above described water to be frequently used. One of these schemes insists more upon the manurial value of sewage, the other looks only to its purification. The former is known as Broad Irrigation. By this process, the sewage being conducted to land prepared for the purpose, is suffered to flow over it and be taken up in part by the crops raised upon it. In short, it is an attempt to extract the element of value from the sewage by using it as a fertilizer in farming. The noxious and offensive elements are thus either beneficially appropriated by crops, or are detained in the soil by mechanical filtration, or, by long and repeated exposure to the air are decomposed, oxidized, and changed into harmless matters, so that the water which runs off is comparatively pure. More than one hundred towns in England employ this system, and it proves eminently satisfactory where conditions favor its adoption. Its great drawback is the vast area of land required for its successful operation on a large scale. It is stated, for example, in our engineer's report, that Boston would require a farm about as large as the entire township of Brookline, if it wished to realize the whole farming value of its sewage. The best English authorities estimate that one acre of land must be set aside for each one hundred persons. When it is remembered that this land must all be tolerably level and fairly dry, some appreciation is reached of the obstacle which this incident presents to the general adoption of this system. There are subsidiary difficulties which will naturally occur to all. It suggests alarming possibilities of farming on a large scale, by municipal corporations. This prospect may well damp the enthusiasm of many who would eagerly welcome such a solution of the sewage problem, if sufficient private farming enterprise were available upon tracts of land convenient and adapted to the purpose. If only the farmers stood ready to take all that might come in every hour of the year, the case were simple enough; but here lies the difficulty. This system proper does not contemplate running to waste any part of the sewage. And this circumstance is important because any elasticity just at this point would materially accelerate its welcome in New England. For weeks, and sometimes months, of our summer droughts, this dirty water charged with stimulating substances might be invaluable to men who had learned how to use it to best advantage. But that is not the proffer which we have to make when we lay out an irrigation farm. Dry or wet, night and day, summer or winter, the same quantity must be taken, or, if there be any variation it is likely to be most when the crop needs it least. And it is this obligation which we fancy would dismay our farmers. But in the absence of such a private demand, it is difficult to see how the work can be carried out without the gation. Having no crop to consider, direct intervention of the municipality. much less land will suffice, as it is found Now, there are manifest and weighty ob- that the ground will filter ten times as jections to superadding such delicate much sewage as any crop upon it can functions to the already onorous duties profitably absorb. Having no farming imposed upon our town and city govern- ventures at stake, we are relieved of all ments. Even apart from the considera- the machinery of trade and difficulties of tion that they seem already sufficiently management. Purification, not profit, is burdened, it is not probable that such the paramount idea. Not that it is immanagement could be made tolerably possible, in certain cases, to combine economical in the long run, to say noth- some profitable use with this primary ining of any profit, but it may be said that tention, but if so, it is a purely secondsuch a farm ought to command a rent, ary consideration. This system is, in if there is really value in sewage. Pos- effect, nothing but turning certain tracts sibly this may turn out on trial to be the of suitable land by skillful preparation, case. The farm at Pullman is asserted into monstrous filters. There is propto have more than paid expenses at times. erly no attempt to save any matters held but we have no evidence as yet that in suspension or solution in the sewage. private capital is convinced of the prac- The object is to get clear of them utterticability of making a profit from such a ly, whether they be good or bad, precious contract, and even if it were, tenants of or worthless, and restore the water to its such farms would require vigilant watch- first estate, pure and undefiled as it ing lest they turn away unwelcome sew- bubbled from the spring. And this wonage into the nearest water-course. derful transformation is confidently asIn fine, we believe this system to be serted to be brought about by a faithful admirable, if only a number of somewhat application of the filtration process. Its intractable conditions, some of which we advocates maintain that sewage passed have indicated, can be controlled. Where through ten feet of prepared earth is all things can be made to work together good enough for any purpose, and they in harmony it offers a reasonable proba- claim it to be nature's process, and intibility of at least reducing the expense of mate that, after all, it is a mere question getting rid of sewage to a minimum of a little more or less remoteness, and Where an arrangement can be made to every drop of water on earth to-day was operate it in combination with filtration, sewage not long ago. However that may so that private agriculturists may take be, it is sufficient for the present purpose the sewage in such quantities, and at to say that if properly managed it does such times as they may find best for afford a practicable, economic and effitheir crops, and when not desired can cient means of cleansing sewage. The turn it upon filter beds, we think there objections to it are fivefold. It is would be a fair prospect of attaining the charged to be wasteful in that it feeds no largest measure of utilization with the crop. There is a dread lest so much least possible complication and expense. sewage on so little land should cause ofThe second of these plans is known as fence, especially in midsummer. Doubtas Intermittent Downward Filtration ers are confident that the land must through porous land. Intermittent fil- eventually clog. And, finally, it is tration, pure and simple, is the converse thought that the cost of the preparation of irrigation. The latter is the mininum of the land will be excessive, or that the quantity of sewage applied to the maxi- carelessness to be bargained for with ormum area of land, and permits utiliza- dinary management on a large scale tion, as well as purification to the greatest would render its success utterly probdegree. The former is the application of lematical. The final arbiter of all such the maximum quantity of sewage upon questionings is experience, and that inthe minimum area of land. It permits fallible test has decided that these fears of only partial utilization, but in our are for the most part groundless. The opinion of more perfect purification. It frankly abandons all dreams of profit, and in so doing it gets rid of the two greatest drawbacks to the system of irri first cost of preparing the land is doubtless likely to be considerable, but as so much less land will answer the purpose, there is found to be a large saving on |