Mem

By a statement in the By-Laws of the association (Art. X., Sec. 1), "only members who have paid their dues shall enjoy the privileges of the meetings." The three general sessions will be the only occasions for any restriction of admission at the Chicago meeting. bers in good standing and associates for the meeting will enjoy all the privileges, including the general sessions. As set forth in the preceding section of this announcement, registered members and associates are to have the privilege of introducing guests for the general sessions. Members of associated societies who are not members or associates of the association are guests of the association for the three general sessions, but they do not have the privilege of introducing guests.

Students actually in attendance at the University of Chicago are to be guests of the association, in the same way as are members of associated societies. Others may receive the privilege of the general sessions by applying in the registration room, but it is hoped that the cooperative nature of the association will lead most persons of this group to become either members or associates. It is to be remembered that the work of the association requires funds and that the only available source of funds for this work is the dues paid by members and associates. The association does not wish to restrict the benefits of its meetings, but it must emphasize the fact that these are possible only through the loyal cooperative support of those who are interested in scientific advance and in the spread of knowledge.

Delegates to the Chicago meeting from scientific and educational institutions should promptly register as such. They will receive all the privileges of the meeting, as in the case of registered members and associates, except that of voting.

No special program of entertainment for visiting women is planned for the Chicag meeting. The local committee announces however, that Ida Noyes Hall will be open t visiting women throughout the meeting, i cluding the use of the dining and club faci ties of this hall, which is perhaps the fi club for women that has ever been built. V

denser and the permeance of a magnetic air gap (or a magnetic circuit in air) are each one billionth of their respective "shape factors."4

The electric flux from a charge is equal to the charge, and the magnetic flux from a magnetic pole is equal to the pole strength.

The magnetomotive force, per turn, of a coil is equal to the current flowing through it. The electromotive force, per turn, generated in a coil is equal to the rate of change of the flux within it.

The energy of an electric, or magnetic, field is equal to one half the product of the flux and, respectively, the electromotive or magnetomotive force.

"Flow of Heat through Furnace Walls; the Shape Factor," Irving Langmuir, E. Q. Adams and G. S. Meikle, Trans. Amer. Electrochem. Soc., 24, 53 (1914).

sults lately obtained on the atomic weights of the isotopes of lead and of neon indicate that one sixteenth of the atomic weight of oxygen is very near indeed to the unit mass of the Prout hypothesis, but it is highly improbable that it should be identical with it. (It would require that oxygen consist of one isotype only-or a still less probable balancing of heavy and light isotopes.)

The most flagrant case of irrationally related metric units is that of electrical quantity, for which four units, no two of which are commensurable, are in actual use. These four are (1) the electrochemical equivalent of electricity, or Faraday, (2) the coulomb, which is one tenth of the centimeter-gram-second electromagnetic unit, (3) the centimeter-gramsecond electrostatic unit and (4) the "Heaviside" electrostatic unit, differing from the foregoing by the factor 1/V4, and used by Lorentz and others in electron theory calculations in order to give a simple form to the fundamental equations for the electromagnetic field. The ratio of the electromagnetic to the electrostatic unit is numerically the same as the velocity of light, hence a reconciliation is possible only in a system which makes the numerical velocity of light a power of 10. A unit of the Heaviside type is quite satisfactory for practical use,

hence the adoption of such a unit would obviate the necessity of having one unit for theoretical and another for practical work. Finally, by a suitable selection of a unit of mass the electromagnetic and electrochemical units can be brought into harmony. (It should be noted that this involves giving up the use of water as a standard of density.) To summarize: it is possible by making the numerical value of the velocity of light a power of 10, by suitably choosing the unit of mass, and by using the Heaviside definition of unit charge to derive a single unit of electrical quantity suitable for all purposes.

Heat and temperature units are to be derived by purely dynamic definitions, without regard to the properties of the substance, water. Unit temperature is the temperature at which unit concentration of a "perfect gas" exerts unit pressure on the walls of its container; while the difference between the heat capacities of a mol of "perfect gas" at constant pressure and at constant volume is the unit of heat capacity and of entropy.

In Table I. are given the numerical factors which, in various combinations, are involved in conversion between the proposed units and those of the centimeter-gram-second system.

Tables II., III. and IV. give the ratios of the proposed units to those of the metric system-both algebraically in terms of the factors terms listed in Table I., and numerically.

2 The values for the last four are taken from Kaye and Laby's tables.

3 The quantity of electricity required to deposit electrolytically one equivalent of metal. E, the electricity in c.g.s. electromagnetic units per equivalent, is used instead of F, the number of coulombs per equivalent, to avoid mixing engineering and c.g.s. units.

Numerical Value?

12,5664

12.5664

29,986,000,000. cm. per sec.

9,647.2 units per equivalent 83,150,000. ergs per mol per °C. 41,850,000. ergs per calorie

Numerical values are given only when the metric unit compared has a name in common

use.

The names for multiples and submultiples of the fundamental units would be formed with the prefixes now in use in the metric system, e. g., the kilo-unit of electric current and the mega-units of pressure and of temperature would probably be used more than the fundamental units; but, aside from the preference of one multiple or submultiple to another, the

units in engineering and scientific work would be identical.

The advantages to be gained are indicated by the following statement of some of the points of difference from both the English and the metric system. In the proposed system: The fundamental unit of capacity (liquid measure) is the cube of the unit of length.

Astronomic units of distance now in use, "light second," "light hour," etc., are commensurable with the units proposed, the first being one billion times the fundamental unit of length.

Under "standard conditions" one mol of "perfect gas" occupies unit volume.

The difference between the specific heats of a "perfect gas" at constant pressure and at constant volume is 1.

Unit current in electrolysis deposits per second one billionth of an equivalent of metal. The electrostatic capacity of an air con

denser and the permeance of a magnetic air gap (or a magnetic circuit in air) are each one billionth of their respective "shape factors."4

The electric flux from a charge is equal to the charge, and the magnetic flux from a magnetic pole is equal to the pole strength.

The magnetomotive force, per turn, of a coil is equal to the current flowing through it. The electromotive force, per turn, generated in a coil is equal to the rate of change of the flux within it.

The energy of an electric, or magnetic, field is equal to one half the product of the flux and, respectively, the electromotive or magnetomotive force.

"Flow of Heat through Furnace Walls; the Shape Factor," Irving Langmuir, E. Q. Adams and G. S. Meikle, Trans. Amer. Electrochem. Soc., 24, 53 (1914).