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Preheating.--The practice of heating the metal around the weld before applying the torch flame is a desirable one for two reasons. First, it makes the whole process more economical; second, it avoids the danger of breakage through expansion and contraction of the work as it is heated and as it cools.

When it is desired to join two surfaces by welding them, it is, of course, necessary to raise the metal from the temperature of the surrounding air to its melting point, involving an increase in temperature of from one thousand to nearly three thousand degrees. To obtain this entire increase of temperature with the torch flame is very wasteful of fuel and of the operator's time. The total amount of heat necessary to put into metal is increased by the conductivity of that metal because the heat applied at the weld is carried to other parts of the piece being handled until the whole mass is considerably raised in temperature. To secure this widely distributed increase the various methods of preheating are adopted.

As to the second reason for preliminary heating. It is understood that the metal added to the joint is molten at the time it flows into place. All the metals used in welding contract as they cool and occupy a much smaller space than when molten. If additional metal is run between two adjoining surfaces which are parts of a surrounding body of cool metal, this added metal will cool while the surfaces themselves are held stationary in the position they originally occupied. The inevitable result is that the metal added will crack under the strain, or, if the weld is exceptionally strong, the main body of the work will he broken by the force of contraction. To overcome these difficulties is the second and most important reason for preheating and also for slow cooling following the completion of the weld.

There are many ways of securing this preheating. The work may be brought to a red heat in the forge if it is cast iron or steel; it may he heated in special ovens built for the purpose; it may be placed in a bed of charcoal while suitably supported; it may be heated by gas or gasoline preheating torches, and with very small work the outer flame of the welding torch automatically provides means to this end.

The temperature of the parts heated should be gradually raised in all cases, giving the entire mass of metal a chance to expand equally and to adjust itself to the strains imposed by the preheating. After the region around the weld has been brought to a proper temperature the opening to be filled is exposed so that the torch flame can reach it, while the remaining surfaces are still protected from cold air currents and from cooling through natural radiation.

One of the commonest methods and one of the best for handling work of rather large size is to place the piece to be welded on a bed of fire brick and build a loose wall around it with other fire brick placed in rows, one on top of the other, with air spaces left between adjacent bricks in each row. The space between the brick retaining wall and the work is filled with charcoal, which is lighted from below. The top opening of the temporary oven is then covered with asbestos and the fire kept up until the work has been uniformly raised in temperature to the desired point.

When much work of the same general character and size is to be handled, a permanent oven may be constructed of fire brick, leaving a large opening through the top and also through one side. Charcoal may be used in this form of oven as with the temporary arrangement, or the heat may be secured from any form of burner or torch giving a large volume of flame. In any method employing flame to do the heating, the work itself must be protected from the direct blast of the fire. Baffles of brick or metal should be placed between the mouth of the torch and the nearest surface of the work so that the flame will be deflected to either side and around the piece being heated.

The heat should be applied to bring the point of welding to the highest temperature desired and, except in the smallest work, the heat should gradually shade off from this point to the other parts of the piece. In the case of cast iron and steel the temperature at the point to be welded should be great enough to produce a dull red heat. This will make the whole operation much easier, because there will be no surrounding cool metal to reduce the temperature of the molten material from the welding rod below the point at which it will join the work. From this red heat the mass of metal should grow cooler as the distance from the weld becomes greater, so that no great strain is placed upon any one part. With work of a very irregular shape it is always best to heat the entire piece so that the strains will be so evenly distributed that they can cause no distortion or breakage under any conditions.

The melting point of the work which is being preheated should be kept in mind and care exercised not to approach it too closely. Special care is necessary with aluminum in this respect, because of its low melting temperature and the sudden weakening and flowing without warning. Workmen have carelessly overheated aluminum castings and, upon uncovering the piece to make the weld, have been astonished to find that it had disappeared. Six hundred degrees is about the safe limit for this metal. It is possible to gauge the exact temperature of the work with a pyrometer, but when this instrument cannot be procured, it might be well to secure a number of "temperature cones" from a chemical or laboratory supply house. These cones are made from material that will soften at a certain heat and in form they are long and pointed. Placed in position on the part being heated, the point may be watched, and when it bends over it is sure that the metal itself has reached a temperature considerably in excess of the temperature at which that particular cone was designed to soften.

The object in preheating the metal around the weld is to cause it to expand sufficiently to open the crack a distance equal to the contraction when cooling from the melting point. In the case of a crack running from the edge of a piece into the body or of a crack wholly within the body, it is usually satisfactory to heat the metal at each end of the opening. This will cause the whole length of the crack to open sufficiently to receive the molten material from the rod.

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There is no Scripture story better known than that of Naaman, the Syrian. It is memorable not only because artistically told, but because it is so full of human feeling and rapid incident, and so fertile in significant ideas. The little maid, whose touch set in motion this drama, is an instance of the adaptability of the Jew. Nothing seemed less likely than that this captive girl should carry with her into Syria anything of much value to anyone. Possessions she had none. Friends she might have, only if she could make them. As a captive in a foreign land she might reasonably have put aside all hope of obtaining any influence, and might naturally have sought only to benefit herself. But she was a girl with a heart. She at once took an interest in her new home, and saw with sorrowful surprise that wealth could not purchase immunity from participation in the ordinary human distresses, nor guarded gates forbid disease to pass in. Brooding from day to day over the stories she had heard of Elisha’s power, and listening to her mistress’s account of the failure of still another attempted cure, she exclaims with childlike confidence and earnestness, “Would God my lord were with the prophet that is in Samaria! then would he recover him of his leprosy.” And thus her natural interest in the troubles of other people, her cheerful and spirited acceptance of her position, and the sense that taught her to make the most of it, brought her this great opportunity of doing an important service. No one can lay the blame of his uselessness and lack of good influence on his lack of opportunity, if he is in contact with men at all, for wherever there are human beings there are sorrows to be sympathised with, wants to be relieved, characters to be fashioned.

And while this Jewish maid was utilising her captivity, her parents, if alive, would be eating their hearts out with anxiety and anguish, imagining for their daughter the worst of destinies. Instead of the horrors which usually follow such a captivity, she is cared for in a comfortable home. Little did the parents, think that there was any work to be done in Syria, which none could so well do as their little girl. The Lord had need of her, and knew that when the parents heard all they would not resent that their daughter had been thus employed. None of us see much further into the ways of Providence than those parents saw. Now, as then, those who are bound up in one another are separated, in order that ends even more important than the growth and gratification of natural affections may be attained.

Significant, also, is the dismay of Joram, King of Israel, when he received the letter bidding him find healing for Naaman. So little did he believe in Elisha’s power that he concluded the King of Syria sought to pick a quarrel with him by asking him for a favour he knew he could not grant. But while the king is helplessly tearing his clothes in a passion of despair, Elisha sends him a message which, at least for the present, gives him some calmness: “Why hast thou rent thy clothes? Let him come now to me, and he shall know that there is a prophet in Israel.” Elisha is ashamed that the King of Israel should have exhibited such weakness before a foreign potentate. He feels that the honour of Israel’s God is implicated, and boldly takes upon himself the responsibility of the cure. Bold it certainly was, and tells of a confident faith that God will be faithful to His servants. The king had no such faith. There was a power resident in Israel of which he took no account. Like many other governments, this Israelitish monarchy was unaware of its own resources, because it did not condescend to reckon what was spiritual. Frequently in civil history you find governments brought face to face with matters for which they are, with all their resources, incompetent. In modern Europe, and as much in our own country as in others, everything gives place to politics. Nothing stirs so much excitement. Differences in religion do not sever men as differences in politics do. We should, therefore, recognise what is here suggested, and should counter-balance an undue regard for political movements and political power by the remembrance that the hardest tasks of all are accomplished by quite another power, and by a power which the politician often overlooks. What have we seen time after time in our own Parliament, but the civil power rending its garments over evils which it cannot cure? Are not the remedies which have been proposed for prevalent vices absurdly incompetent? And it is the Church’s shame if she cannot step forward and confidently say, You cannot deal with such things; hand them over to me. There must always be “distempers of society” which rot the very life out of a nation, and for which legislation and criminal law are wholly inadequate. Honest-minded men who will not trifle with alarming abuses, who will not pretend they have found a remedy, must simply rend their garments in their presence. And it is well that in our day, as in others, there are men who, trusting in personal effort and Divine aid, practically say to Government, “leave these things to us.” Christian charity and practical wisdom have, in our day effected a good deal more than the healing of one leprous grandee, even if as yet the spiritual force that resides in the community is only spasmodically and partially applied to existing evil.

Elisha’s treatment of Naaman was intended to bring him into direct and conscious dependence on God; or, in other words, to produce humility and faith. Some persons are crushed and mastered by pain and sickness, and some gain in spiritual worth what they lose in physical strength. But Naaman’s disease had as yet done little to instruct him. He came as a great man, with his servants, and chariots, and piles of money, to purchase a cure from a skilled man. He did not see what Elisha plainly saw, that if this blessing came at all, it must come from Israel’s God, and that with Jehovah no man Could barter or be on bargaining terms, but must accept freely what was freely given. Therefore Elisha refuses even to see him, that Naaman might understand it was with God he had to do; and by refusing a single penny of payment he compelled the Syrian to humble himself and accept his cure as a gift.

And probably the incident finds a place in the sacred history because it marked an important step in the knowledge of God. It was an early instance of the Conquests which the God of Israel was to make among the heathen, a distinct and legible proof that whoever from among the outlying nations appealed to Him for help would receive the blessing he sought. But it was more than this, it emphasized the freeness of all God’s gifts. Nothing could be purchased from Jehovah; everything must be received as a gift. This was a new idea to the heathen, and probably to many of the Israelites also. Certainly it is an idea that is only dimly apprehended by ourselves. Our dealing with one another is to so large an extent governed by the idea that nothing can be had for nothing, that we carry this idea into our dealings with God, and expect only what we can earn and claim. It is a wholesome pride that prompts us to work at anything rather than be dependent on other men, but it is a most unwholesome and ignorant pride that forbids us to acknowledge our dependence on God, and to accept freely what He freely gives. Until we learn to live in God, to own Him as alone having life in Himself, and to accept from Him life and all that sustains it, both physical and spiritual, we are not recognising the truth and living in it. Our good deeds and good feelings, our repentances and righteous intentions and endeavours, are as much out of place as a means of procuring God’s favour and help as Naaman’s talents of silver and pieces of gold. We have God’s favour irrespective of our merit, and we must humble ourselves to accept it as His free gift, which we could not earn and have not earned.