ing the method they now use, every one has the best method, and yet I find that there are no two of them alike, and I think it would be an interesting subject for some one to investigate the method of charging a cupola furnace to see if there could not be a more uniform system applied to it.

Mr. W. F. Durfee.-I have recently been making some studies on the subject of the construction of cupolas, and in connection therewith I have run across a very able paper by a French engineer (M. A. Gouvy, Jr.), and of which I have made a translation, which is about being published in the journal of the Franklin Institute. I think that paper embraces the most complete history of the progress of the development of cupola construction which has yet been written. There is no doubt in my mind that the majority of cupolas in use in this country waste more fuel than is necessary to do the work. The amount of carbonic oxide that is seen burning at the throat of most of our cupolas is more than sufficient, if properly consumed, to do the melting in the cupola itself, and the latest improvement in cupola construction abroad has been made with reference to the entire consumption of this carbonic oxide in the body of the cupola. This improvement is the invention of European engineers, Messrs. Greiner & Erpf, and it consists mainly in this: that in addition to the ordinary tuyeres at the usual level, there is a series of vertical pipes connected with the wind box. These vertical pipes are rather small in diameter, and at intervals their upper ends are connected by suitable small tuyeres with the shaft of the cupola. These auxiliary tuyeres, in the case of a 42-inch cupola, are about 15 in number, and the blast is introduced not at any one level, but at a series of points following a helicoidal curve embracing the body of the cupola. The effect on the introduction of air in this way is this, as the carbonic oxide (generated in the cupola by the decomposition of the carbonic acid) rises through the body of the fuel, it meets, from time to time, a sufficient amount of air to consume it, so that in a cupola constructed after this system there is no escape of carbonic oxide at the throat of the cupola at all. The whole mass of the carbonic oxide is consumed in the cupola itself, and in the upper portion of the cupola this consumption of carbonic oxide has the effect of gradually heating up the charge and preparing it for more economical melting when it gets down to the zone of fusion, and I apprehend from the result of my investigations that that is a very important thing. I have such faith in its value that I propose to build a cupola on that system, and if suc

cessful I shall take great pleasure in presenting the results of my experience with it to the society. (Applause.)

Mr. Frank Firmstone.-I would like to ask Mr. Durfee whether the Greiner & Erpf cupola has ever been tried in practice.

Mr. Durfee. In this paper by M. A. Gouvy, Jr., when published in the journal of the Franklin Institute, you will find a table of some thirty odd cupolas of various construction, giving the results of the experience with them all; and among the rest there are some statements in regard to the economies of the Greiner & Erpf system. There is quite a number of those cupolas in operation in Europe.

Mr. Firmstone -Precisely the same scheme has been proposed over and over again for blast furnaces, and has been tried without success. It is exceedingly difficult to see how by attempting to burn the carbonic oxide in contact with the mass of the fuel, thereby raising the temperature of the combustion, you are going to avoid a re-formation of the carbonic oxide. Practically, I should say, it would be impossible to burn carbonic, oxide in the presence of the coal and not have carbonic oxide left in a short time.

Mr. Durfee.—If the blast was introduced at a uniform level, that would be true. But the blast is not introduced at a uniform level. These auxiliary tuyeres effect an entrance into the cupola at successively higher levels, so that the carbonic oxide is continuously burned as it is formed, there being none finally left to be consumed at the throat of the furnace.

Mr. H. H. Suplee.-In this connection I might cite the case of the alteration of a cupola in Philadelphia, in which a second set of tuyeres was introduced-about 18 inches higher than the original set. They were connected with them by separate blast gates so that they could be turned off or on independently, and were pointed downward at a slight angle. The blast was started with the original set of tuyeres, and at a short interval after-I cannot state exactly the time, the blast was turned on to the second set. The idea originated with the foreman of the foundry, who thought he could obtain better results in that way. Although I have no figures, I know that the output and the time were both materially improved, the heat being handled in a shorter time and the cupola being capable of handling a larger charge. They built an entirely new set of tuyeres, with connections, in a separate box, built about the base of the cupola about 18 or 20 inches above the original tuyeres, introducing the second blast, as Mr. Durfee describes, at a higher

point. This was about three or four years ago. I believe it is still in operation.

Mr. W. M. Barr.-About seven years ago, I built two cupolas for foundry service. As I now recollect them, one was 4 feet in diameter, and the other 5 feet. These cupolas were fitted with a double set of tuyeres, four large ones at the bottom, and, I believe, nine at the top. The distance from center to center being about 18". The object of this double set of tuyeres was to obtain a better combustion than was thought to be possible with one set.

It is well known that carbonic acid gas is the product of perfect combustion. This gas in passing up through an incandescent body of fuel will take up additional carbon, and is thereby changed into carbonic oxide gas. These upper tuyeres were intended to supply air, and by means of a second zone of combustion re-convert the carbonic oxide gas into carbonic acid gas, and thus effect a saving of some 10,000 heat units per pound of coal, and take advantage of the heat thus obtained to increase the efficiency of the cupola. Both of these cupolas were very successful in their operation, and a very considerable economy was had by this arrangement of tuyeres, the result being a melting of about ten pounds of iron per pound of Connellsville coke. This is about three pounds more than I had been able to obtain on an average with single tuyeres. The working of the cupola was satisfactory, but it did not wholly prevent the formation of carbonic oxide gas, but as this gas was formed above the second zone of combustion, we cared but little about it, because the work was practically accomplished, and the little loss of heat which occurred was of no consequence.

Mr. Durfee. The results which have been described by Mr. Barr were doubtless due to the combustion of a large proportion of the carbonic oxide generated, and the reason why the carbonic oxide was not all consumed was because the air was introduced at a fixed plane. In order to consume all the carbonic oxide it is necessary to introduce air continuously at varying levels, so that as fast as the carbonic oxide developed by the decomposition of the carbonic acid is formed, it meets with air to reconvert it into carbonic acid again, which operation must be successively performed in order to consume the whole of the carbonic oxide developed.

CCCXV.

ELECTRIC WELDING.

BY C. J. H. WOODBURY, BOSTON, MASS.

(Member of the Society.)

THE Smith is the highest type of handicraftsman; he alone of all artisans making his own tools and also those of others, commands the dependence of all upon his offices. His work is prehistoric, reaching beyond records or traditions and known to have existed in still earlier times through the personifications of mythology, wherein Vulcan was essential to other divinities. The blacksmith is a factor in every stage of the history of mankind; and his work is now, and always has been a matter of individual skill depending upon a keen eye and steady hand, with a fine sense of form and dimension, untouched by the flood of invention which has modified or even recast other methods of production.

It is true that machinery is used in welding, but it is merely devoted to the application of power to supplement the limits of human strength; and with trip-hammer and crane the same skill is necessary as with hammer and anvil.

Since the first of the year there has been a commercial application of electric welding, the invention of Prof. Elihu Thomson, which has already reached a degree of importance sufficient to render it a live issue in every branch of manufacture to which it has been shown to be applicable.

This process is a new art, for unlike the smith who is confined to iron, steel and platinum, it can weld any two pieces of the same metal or alloy ranging from the most refractory metals to the alloy which fuses at 162° Fahr. It will join dissimilar metals when the welding point of one is not too far in excess of the fusion point of the other.

These results seem to indicate that the classification of metals into welding and non-welding has been due to imperfections in the ordinary and time-honored methods, rather than any peculiarity in physical constitution warranting such arbitrary classification.

It is true that some of the metals have been joined without sol

der by means of the autogenous soldering process, wherein local fusion is produced with an oxyhydrogen blowpipe, but that laboratory experiment is not a union of metals heated to a plastic condition which precedes fusion, according to the accepted meaning of welding.

Passing by the scientific interest of electric welding, a short allusion will be made to the principles upon which it is based as preliminary to a description of the apparatus, and then consideration will be given to its practical applications.

THE PRINCIPLES.

All forms of matter possess in varying degree the susceptibility of permitting the molecular motion necessary for the transfer of electric energy; those whose characteristics are favorable for such motion being termed, conductors, and those which do not readily permit such motions are called non-conductors or insulators; and various adjectives are frequently used to express in a general way some sense of their value, but throughout the whole list of all known matter, there is some measure of conductivity, and the whole expression is one of degree; the conductivity of silver, for example, being over one hundred billion times that of glass; and other materials possess measures of conductivity lying between these extremes. The ability of any body to conduct electricity in comparison with others of its kind is directly as the area of the cross section and inversely as the length.

Whenever electricity is provided with what is termed a good conductor, it makes no manifestation of its presence, but if there is poor conductivity by reason of small cross section or poor conductivity of the material, there is resistance to the electricity. Then a portion of the electric energy is expended in producing excessive molecular motion, and converted into heat, which is radiant if the temperature is high enough, as in the case of the incandescent light, when the metal portion of the circuit possesses ample conductivity to carry the electricity without appreciable heating, but the carbon filament in the lamp is a poor conductor, both in regard to physical characteristics of the material and small cross section, and the molecular motion is so violent as to produce a temperature sufficiently great to contain light rays.

The total amount of mechanical work done by a current C in overcoming a resistance R during a time T, is RCT; and the