"The repairs on steam boilers must generally be done in a small space. The welder requires the welding apparatus as near as possible, and as the space available prevents the fixing of a cumbrous apparatus, it remains only to use one as small as possible, which will, however, by reason of the great strain it will be exposed to, deliver bad gas. The first condition for repairs on steam boilers is therefore to abandon the generators, as they cannot under the circumstances produce the quality of the gas as required. When, on the other hand, acetylene-dissous is obtainable, then a pure and cold gas can be used at any place.

"2. Another not less important point is the blowpipe. It can be proved in most instances that the blowpipes obtainable at the lowest price are those generally used. The conditions as to quality have not yet been extended to blowpipes.

"A satisfactory blowpipe should fulfil the following conditions: -

"(a) The gases must remain mixed in proper proportions.

"(b) The gases must leave the burner with a certain velocity, so as to keep the metal fluid, without chasing the metal.

"(c) The flame must, in certain welding operations, have a pressure sufficient to prevent the melted metal to drip from the weld. All burners working with oxygen under pressure and acetylene without pressure become after a short time of working useless. The radiating heat affects the oxygen, which is under pressure, with great velocity in a narrow space, in a different way than its action upon the acetylene contained in a larger space and without pressure. The result is a decomposition of the flame and a burning of the metal. This can only be prevented by a skilful welder. It is therefore a difficult task to produce a burner in which the gases are kept under pressure in such a way so as to offer the same results in respect of expansion.

"3. If the technical conditions have been fulfilled and the acetylene-dissous is to be manufactured in Germany, the remaining condition of supplying a sufficiently trained staff offers very great difficulties. Le Chatelier, Marseilles, for instance, does not permit any of his mechanics to even attempt to make a weld unless he has had at least six months' training at the works.

"I wish to contradict the statement made that it would be impossible to make a perpendicular weld or one in a roof, as not only could such a defect be repaired by welding, but the mechanic could even remain resting on his back repairing any defects above him. The welding under such circumstances must of course be made by means of suitable burners, so as to prevent the melted metal from the welding rod to drip. It is often necessary to have the welder trained for weeks in the dark to enable him to judge the flame, and to prevent its decomposition, as repairs on steam boilers are generally made in the dark and not in a well-lighted workshop. The welder should also be prevented from long continuous working, as the faintest shake of the blowpipe may often result in an unsatisfactory weld; he must, of course, be paid accordingly. The firm undertaking repairs on steam boilers must be provided with a skilled staff of workmen, in interest of public safety.

"4. Another important point in the production of a satisfactory weld is the composition of the welding rod from the metal of which the crack or defect is to be filled. Based upon my own experience and upon the results obtained, the size of the welding-rod plays also an important part.

"5. The last, but not the least, important part is the completion of the weld by mechanical means, such as hammering or otherwise. The technical and ingeniously arranged mechanical appliances in this respect, as used by Le Chatelier and others, and being the sine qua non of a satisfactory weld, are naturally withheld from inspection by competitors. It may, however, be stated that the said means consist of hammering and annealing, means which are also being used in welding by water-gas. So far as annealing is concerned, my own examinations tend to show that it has no influence upon the strength and elasticity, but produces a more homogeneous weld.

"How far these conditions may assist in the production of a satisfactory weld, experience and tests alone can show. There is reason to believe that such tests will be carried out in Germany within a reasonable time and on a large scale by proper authorities, not merely on test rods in the laboratory but upon actually welded articles. The importance of such tests cannot be over-estimated."

The Chemische Fabrik Griesheim-Elektron, carrying on hydrogen welding on a large scale, in a recent letter addressed to the Bayerischen Revisions Verein, say: -

"Repairs on steam boilers by means of autogenous welding should be prohibited, because a perfect weld can only be produced on a horizontal and easily accessible surface. Corrosion on a perpendicular surface cannot, in general, be welded satisfactorily ; besides, the plates are generally of a thickness of more than 10 m.m., and by such thickness an unsatisfactory weld only can be the result, even with the acetylene flame, which produces a flame of considerable heat. It is evident that by means of this kind of welding, a perpendicular or overhanging weld cannot be done. Independent of the unsatisfactory repairs of steam boilers by means of welding, very few suitable opportunities would be offered."

C. L. J. Hartmann, an authority in Hamburg, in a letter dated 22nd April, 1908, says: "Electric welding has for years been used here for repairs on marine boilers with great advantage. It must, however, be stated that the respective firms using the system are fully conversant with boiler making. Experience has also here proved that attempted repairs of tension cracks have been unsatisfactory.

"I take as great an interest in autogenous welding as in any industrial development, and I truly hope that it will, besides the electric welding, bring advantages to the shipbuilding, but without injury to public safety. Precaution is, however, advisable, and it is necessary to be careful not to embark upon an insecure territory, otherwise the reaction will not fail, and the autogenous welding will disappear as quickly as it came."