greater amount of power, without increase in the amount applied.

Mechanical Stokers on Locomotives

Question: Have experiments been tried with mechanical stokers on locomotives? If so, why is their use not practicable?-E. W. C.

Answer: Owing to the fact that there are so many faults in their mechanical construction, these stokers have not proved very efficient, except in the case of slow firing. Where rapid firing is required, as on locomotives, it would hardly be practicable to use them.

Specific Gravity of Electrolyte Question: The weight of the electrolyte in a storage cell of the E II Chloride Accumulator type, is 26 pounds. I find the specific gravity of the electrolyte, when cell is fully charged, to be 1.205. How much pure water (specific gravity 1.000) must be added to make the specific gravity of the electrolyte 1.200?— M. D. H.

Answer: This calculation may be made as follows: Let r equal the volume of water; and let y equal the volume of the electrolyte. Then we can form the equation:

Adjusting Current for Fan Motor

Question 1: What effect would an alternating current at 110 volts and a frequency of 60 cycles have on a fan motor designed for 52 volts and 125 cycles?

Question 2: What effect would it have on one designed for 110 volts and 125 cycles?

Question 3: What device can be used to adjust the difference?

Question 4: How does the choke coil in an alternating enclosed-arc lamp adjust the frequency of the current?-J. B.

Answer 1: It would cause the motor to heat very badly, because both the magnetic flux and the current would be high. Also, the speed would be decreased approximately one-half.

Answer 2: Heating would occur, but to a less extent than in the first case. The speed would also be decreased to about one-half.

Answer 3: In supplying 110 volts to the 52-volt motor, you could use a resistance to cut down the voltage to the proper amount; but there is no practicable way of compensating for the difference in frequency.

Answer 4: The choke coil in an alternating enclosed-arc lamp does not adjust the frequency of the current, but must itself be adjusted to suit the frequency. If the frequency is low, more turns must be used; and if high, fewer turns must be used.

as to prohibit any known method of providing a working contact. All possible designs of rotary engines have seemed to er body essentially a variety of evils, such as unbalanced lateral pressures exerted upon large areas of the revolving part; wasteful port passage and cylinder clearance; contracted passages requiring steam to flow at impossible rates; mutually acting cycloidal members subject to heavy unbalanced pressures tending to force them apart; sliding vanes or wingpistons subject to centrifugal strains with consequent excessive friction and vibration.

Many mechanisms have been constructed; but the long record of failure. has led most practical engineers to believe that the problem cannot be solved in the present state of mechanical development. The distinct advantages of the rotary type are so obvious that new designs are constantly being turned out, and there is reason to think that improvement will go on steadily until satisfactory results are obtained.

Storage of Explosive Mixtures

Question: Can a tank be filled from the explosion of gas or gasoline to a reasonable pressure, say 200 pounds to the square inch? If so, can that pressure be carried to the piston head in a cylinder? If so, what per cent of loss would there be in so doing? If neither can be done, please explain why not.-A. C.

Answer: The tank can be filled with a mixture of gas and air, and the mixture exploded. This would cause a rise of pressure, and, if the pressure were carried to a piston in the cylinder, work could be done. The general principle of the action is the same as that in the ordinary gas engine of to-day, except that the explosive charge is not compressed before explosion. For ordinary operations, the action referred to would not be practical. In the first place, if a large amount of energy is to be stored, the tank would necessarily be of large proportions, and, as the pressure rises, the mechanical difficulties would be almost too great to be overcome. Again, when the mixture is exploded, not only does the pressure

rise, but the temperature also rises to a very high point. It would be impossible, economically, to keep this heat from being lost. This loss of heat which would take place constantly, would affect the economy and would make the whole operation inefficient. This system is quite similar to the method of using compressed air. We have reference to the storage of air in tanks from which it is fed to the cylinders of engines and performs work in the same manner as steam in expanding.

Wiring of Packing Plant

Question: I have a packing house to be wired. It was formerly wired with weatherproof wire supported on porcelain insulators. The rosettes, insulators, and wires next to the insulators, became covered with sait, which caused the wire to be grounded. Would it be advisable to incase the wires in an approved moulding with shellac, or would it be better to expose the wires supported on porcelain?— A. S.

Answer: It would not be advisable to use moulding in this case, as the moulding will absorb moisture, especially in the presence of salt, and will thus become a first-class conductor. It would be better to use approved ceiling rosettes and the best of rubber-covered wire on insulators at the required height. You must, of course, follow the Underwriters' rules for wiring in damp places, using keyless sockets and approved construction throughout.

Size of Boiler Safety Valves Question: What is the proper size of safety valves for boilers?-R. S. D.

Answer: Three square feet of grate surface is usually allowed for one inch area of spring-loaded valves, or two square feet of grate surface for one inch area of common lever valves.

Nurnberg Gas Engine

Question: Is the Nurnberg Gas Engine single- or double-acting, and on what principle do the cylinders work?—G. J.

Answer: The formula (a) is approximately correct, and agrees very closely with the one given in Kent on page 294, but in a different form. This formula is derived as follows: Assuming any length of the section, as N, shown in the sketch, we have for the total resistance of the same N× × 2 × 48,000 × .6. The section of the metal on each side of the tank is Nxt; and, since there are two sides, the total section is 2 x N x t. Allowing a tensile strength of 48,000 pounds per square inch and an efficiency of 6 for a double-riveted lap joint, the total strength of the section of the tank mentioned is expressed as above. The terms and N are each expressed in

inches. The total strain on this section due to water of a head of H feet, is H x .433 × N × 12 D. N is in inches as before, but H and D are in feet. Each foot of water corresponds to a pressure of -433 pound per square inch. Therefore the total pressure on the section under consideration is H x .433 pounds. This is assuming that the maximum pressure is exerted throughout the length of the strip N, but of course it would not be quite as great at the top of the strip as at the bottom. The total pressure acting across a diameter, then, is H × .433 × N x 12 D. Allowing for a factor of safety of 4, the total strain on the section N must be equal to 4 of the resisting power of the metal. We have, therefore: NXX2×48,000×.6 4

Solving,

=HX.433XNX12D.

International Electrical Congress

THIS important gathering, which met at St. Louis, Mo., September 12 to 17, was a pronounced success, not being surpassed by any of those which had previously convened for similar purposes. A joint meeting of the American Institute of Electrical Engineers and the Institution of Electrical Engineers of Great

Britain was held in connection with the Congress. The total number of registered delegates was in the neighborhood of 900, of whom more than 700 were in attendance; and a total of 160 papers was read.

These papers had been planned with great care, and each one prepared by a recognized authority on the respective subject. The transactions of the Congress, which will be published later and distributed to the members, will contain all these papers and will form an extremely valuable volume. The papers were selected by the committee in charge, so that the authors represented as many different countries as possible, thus giving the broadest possible view of the various subjects discussed, and also giving a really international aspect to the transactions.

The Congress was divided into eight sections in order to facilitate the work. Wednesday, September 14, was "Electricity Day" at the Fair. There was no meeting of the Congress on this day, which was given over to a joint meeting of the American Institute of Electrical Engineers and the Institution of Electrical Engineers of Great Britain. President Arnold of the former society gave his presidential address, in which he took up the probable future electrification of steam railways.

Among the prominent men who presented papers may be mentioned Mr. B. J. Arnold, Dr. Louis Bell, Prof. J. C. Kelsey, Mr. Philip Dawson, Mr. Kempster B. Miller, and Prof. C. P. Steinmetz. Mr. Kempster B. Miller's paper, which has since been published in various telephone and other electrical journals, was on “Auphony," and embodied an exceedingly tomatic vs. Manual Systems of Teleable discussion of this most timely topic.

A Chamber of Delegates was formed on the first day of the convention. The following officers were elected: President, Prof. Elihu Thomson; Secretary, Dr. A. E. Kennelly; Assistant Secretary, Dr. F. A. Wolff, Jr. This Chamber of Delegates did not take any definite action with respect to units and standards; but, by unanimous vote, it was decided to appoint an International Governmental Commission to deal with the matter of electro-magnetic units. A resolution was societies of the world should appoint an also adopted that the various technical International Commission to take up the work of standardizing the nomenclature and readings of dynamo-electrical apparatus and machinery.

Wireless Telegraphy

THE successful transmission of messages by the DeForest wireless telegraph between St. Louis and Chicago on September tember 14, "Electricity Day" of the World's Fair, marks an epoch in the history of space telegraphy, as this is the longest land distance yet covered. The long-distance telephone was used to corroborate the telegraph messages, and two members of the award jury were in Chicago as witnesses, while many delegates

ern five-story structure, being constructed of pressed brick, steel, and concrete, with stone trimmings and an ornate porte-cochère. In style and equipment it is of the best. Especial care has been taken in heating, ventilating, and sanitation.

The motor room is located in the basement of the building, and is equipped with the most modern machinery. The electric current used in the building is three-phase alternating, and comes from the power plant three blocks away. By means of transformers it is stepped up from 220 volts at the power plant, to 2,200 volts over the wires, and back to 220 volts at the office.

There are two 30-horse-power motors running two fans which supply the office with fresh air. The air is admitted through a large chute from the roof, which has two coils for tempering the air as it comes in. There is a 5-horsepower motor that runs a 4x6 triplex pump, which pumps calcium chloride through the brine pipes for cooling purposes; also one 10-horse-power motor for a 52x8 triplex pump, for pumping water to the 3,000-gallon reservoir which is used to supply the restaurant and for other various uses. This tank is emptied