Company, and later a similar exhibit was given at Lynn, Mass., by the General Electric Company, the former by bi-phase generation and transmission, the latter by tri-phase.

After a most careful study of the subject from a scientific and commercial point of view, the bi-phase system of twenty-five alternations per second was adopted by the Cataract Construction Company. When such a low rate of alternation was discussed, it was apprehended that the cost of static transformers would be so much increased as to more than counterbalance the efficiency promised by the lowering of the rate of alternation; but, as in many other cases, when a want is felt, the urgency of the want leads to improvements that entirely change the conditions; so in this case, while many predicted that static transformers of this low period would cost from fifteen to twenty or even twenty-five dollars per horse power, still when tenders were to be solicited a guarantee had been exacted that the price should not exceed five dollars per horse power, while in actual practice, in healthy competition, the machinery for the purpose was secured at a very much lower rate.

As to the results reached by the system adopted, I must call your attention to the remarkable character of the industries that clustered about the central station. In 1893 there were no biphase motors of high efficiency manufactured, as up to the last few years alternate-current electric lighting plants had not been adapted to the operation of highly efficient motors to take the place of steam engines. There were few if any applicants for power to drive machinery. No cotton mills or other textile industries sought cheap power when it involved the use of machinery that had yet to be perfected. Existing direct-current motors could be had in abundance, but manufacturers had not yet used them. The largest cotton or woolen mills required not over 1000 horse power to drive them, while most are on a smaller scale.

The advantages offered by the elastic electric system at Niagara Falls attracted industries that employed few hands, needed little machinery, but required enormous amounts of power, which, at a lower cost than steam and without an investment in engines and dynamos, could be used profitably.

The Pittsburg Reduction Company, engaged in the extraction of the metal aluminum from its ores, was the first applicant for 1500 to 3000 horse-power electric current from the new power-house. This process, known as the Hall process, required heat energy to

melt the cryolite to form the bath in the electric furnace, and a direct current of low voltage to exercise electrolytic energy in separating the metal from bauxite, which is rich in aluminum. Another enterprise, the Carborundum Company, called for 1000 horse power, in alternate current of one phase only, for a process in which heat energy alone is needed to produce a new mineral next in hardness below the diamond. So with the manufacture of carbide of calcium from coke and lime, great heat alone needed was obtainable by alternate current. The Matheson Alkali Company, making caustic soda from common salt, needed no heat energy, but over 2000 horse power of direct current for electrolytic or electro-chemical energy in a cold process to separate the chlorine gas from the salt water, the gas being delivered into enormous lead-lined chambers, the floor of each chamber being covered with lime, enabled twenty-five tons per day of bleaching powder to be furnished to the market, while the caustic soda liquor, freed from chlorine, is concentrated by boiling in iron kettles to evaporate the water and thus leave caustic soda in solid form when cold. This caustic soda, delivered to still another factory near at hand, is by a direct current, furnishing heat and electrolytic energy, made to yield pure metal sodium, just as Sir Humphrey Davy did when, with the current from a galvanic battery, he produced and gave to the world a few ounces of the new metal. The ingots of sodium, as made by the Chemical Construction Company, at Niagara Falls, are dipped into coal oil and thrown into tin cans, to be closed air-tight, ready for the market, or at once, by a simple process, converted into peroxide of sodium, one of the most powerful oxidizing reagents required in the arts. Factory after factory has been added, for various electro-chemical processes, while the establishments first started have grown in size calling for power in a rapidly increasing ratio.

While these industries were developing, electricity has been furnished to the lighting station to replace steam as the motive power, and a direct current is being delivered to the trolley lines of Niagara Falls and Buffalo. By the time the development was in shape to offer power to Buffalo, and the cost of installation was being worked out there, one great advantage of the tri-phase system over the bi-phase that had been adopted was urged as an important argument against what had been done. This advantage comes from the fact that the bi-phase transmission needs four cables, two

for each phase, while the tri-phase system is worked with three cables only, each of the three cables being no larger than each of the four demanded by the bi-phase system. This advantage had been taken into consideration, but other economies incident to the bi-phase had overbalanced the question of saving in copper in the line. Before the line to Buffalo could be built, however, and as a striking instance of an urgent need of exciting the talent of inventors to supply the want, Mr. C. F. Scott, of the Westinghouse Company, startled the electricians at a meeting in Washington with his scheme of converting the bi-phase current into a tri-phase in the static transformers that are used to raise the electro-motive force of the current from 2200 volts to 11,000 volts or more-this without adding one dollar to the actual cost of the transformers needed, and with the saving of twenty-five per cent. in the copper used, which must be credited to the tri-phase transmission. So that while the low frequency adopted increased the efficiency of the plant, and favored many operations of the power plant, the first cost was not affected by the prophesied high cost of transformers, and all the advantages incident to both systems were obtained not only without an increase of the first cost, but a direct saving in the copper of the line. As the plant grew in size, many of the difficulties that had been expected in handling such an immense volume of electricity as was involved did not occur, and it was evident that the practical electricians attached to the great manufacturing establishments of electrical machinery had brought the appliances needed well up to the requirements of the new conditions. Every machine, every instrument needed, had to be contrived, not only to suit the size of the unit of 5000 horse power, but to meet the unknown effect of coupling so many great machines in parallel and distributing the current to establishments over which the attendants in the power-house have little or no control.

In thus referring to the utilization of power at Niagara Falls, I may seem to depart from the subject of transmission of energy, although the development of the industries described is intended to illustrate the direct results obtained by transmitted energy. The energy developed at the dynamos in the power-house, and existing as potential only while the dynamos are in motion, begins with an electro-magnetic force of 2200 volts, at which 5000 electrical horse power is transmitted by four cables, each 14" in diameter, two cables for each phase of each dynamo, to the bus bars from which the PROC. AMER. PHILOS. SOC. XXXVIII. 159. E. PRINTED JULY 17, 1899.

current is distributed at from 2200 to 2000 volts (depending on distance) to points outside of the power-house within a radius of two miles. By means of step-up transformers 10,000 electric horse power of induced current of 11,000 volts can be carried to Buffalo by six cables, each 5%" in diameter, and capable of transmitting 10,000 electric horse power at the said voltage, or double that amount, at 22,000 volts, with a loss, based on Lord Kelvin's law of economy as to size of conductors.' You can better realize the idea of the size of the conductors when I tell you that from each turbine exerting over 5000 horse power a steel shaft 11" in diameter is needed to drive each dynamo delivering 5000 electrical horse power, from which are carried the conductors of the sizes named. Four bus bars receive the current from five dynamos, the heaviest part of each bus bar being 3" in diameter; i. e., one 11" steel shaft transmits kinetic energy of 5500 horse power; four 14" cables transmit 5000 electric horse power energy of 2200 volts; three 5%" cables transmit 5000 electric horse power to Buffalo.

Besides the development of power at Niagara Falls, to which I have called your attention, numerous successful installations in various parts of our country could be referred to, and even in Europe we find the transmission of power by alternating current in existence, and, in fact, in some instances preceding in actual operation the starting of the plant at Niagara Falls; such installations being on a smaller scale required less time to construct them.

1 Lord Kelvin proposed, in determining the size of conductors for electricity, that the most economical area of conductor is that for which the annual cost of energy wasted is equal to the interest on that portion of the capital outlay which can be considered to be proportionate to the weight of the metal used; that is to say, the amount of copper and other details of the transmission line, the interest of which should equal that amount of energy at its cost of production that may be wasted. The lower the cost of the power generated the more energy may be wasted to advantage. If too large a conductor is installed for the purpose of decreasing the loss, the capital outlay will be needlessly great. If too small a conductor is adopted the waste of energy will be too great, hence the importance of a law that indicates what the economical loss should be. In applying this law there is more or less divergence of opinion as to what part of the capital outlay should be taken into consideration in determining the amount to be wasted. As, for instance, an underground conduit system may be built to accommodate a great increase of the number of conductors installed, or when a pole line is erected for a given amount of power, additional conductors may be supported on the same poles without any great increase of the cost due to enlarging the capacity of the transmitting line. The law, therefore, bears with most force on the metal if naked or the cable if the conductor is insulated.

The experiments of Mr. Tesla, which were directed toward the utilization of an alternate electric current of high frequency, and which were conducted in the interest of the Westinghouse Company, resulted in the issue of at least twenty-nine patents to cover the multiphase generation of electricity. The first of these patents was issued as early as 1888, and the last in 1891, and yet in 1893, so far as I am aware, there were no examples of the Tesla motors in commercial operation, for the reason that up to that time—and, in fact, not until 1895-the conditions had not been favorable to its development. As soon as there seemed to be a demand for their use, however, the manufacturers placed them on the market with as high an efficiency as the best direct-current motors, with this further advantage that is of the utmost importance: A directcurrent motor and a direct-current dynamo are limited in their electro-motive force by the commutator necessary for their operation. The earliest alternating-current motors were what are known as synchronous motors; that is, motors that when started would run in step with the dynamo from which the current proceeded. These motors had no self-starting power, and involved many objectionable features that are not incident to polyphase motors of the induction type-in other words, what we know as the Tesla motor. In the first place, and as of vital importance, a Tesla motor can be wound to suit high voltage. Electricity at 2000 volts can be carried with absolute safety by properly insulated cables into buildings and applied directly to the motor without any live terminals; that is, without any part carrying current being exposed from which a dangerous shock of electricity can be obtained. They are all selfcontained. They start with a powerful torque upon completing the circuit; that is, they start when the switch is closed and stop when the switch is open. Here is the possibility of an ideal electric motor, which is perfectly well understood by professional electricians, but about which the public have yet to be more thoroughly informed.

Though I have said that little was known about the alternating current in practice until lately, yet I have before me a copy of a letter written by Mr. L. B. Stillwell, one of our members, the Electrical Director of the Niagara Falls Power Company, when he was on the staff of the Westinghouse Company, dated May 11, 1893, in which he said: "I received yesterday from our engineer in charge of the installation at Pomona, Cal., a report of tests which he had