me a convenient way of emphasizing and cataloging several important chemical processes. It brings out the effect of conditions on chemical action, conditions which are extremely important and which we are so apt to overlook on account of our system of chemical shorthand. It discloses one of the great problems of chemical research, the discovery of conditions that will make a reaction go to completion in the desired direction successfully and economically, problems which we teachers must present in such a manner that they will serve both as a challenge and inspiration to those boys and girls whom we would recruit as the future leaders in our science.

A GENERAL GAS LAW APPARATUS.
BY JACOB JORDAN,

Oregon Agricultural College, Corvallis.

The apparatus which is described in this article is the result of a request from one of the engineering schools of this college, that the Physics Department include an experiment on the general gas law in its laboratory course.

While there is nothing fundamentally new about the apparatus, the writer has never seen it described or used. This description is given because of the satisfactory results obtained in the freshman laboratory.

As a first attempt an ordinary Boyle's Law apparatus was placed under a sheet iron cylinder closed at the top, and a heating coil was placed inside of the cylinder so that the temperature, volume, and pressure of the air in the Boyle's Law tube could be varied simultaneously. Readings of the temperature of the confined air and of the height of mercury in each arm of the tube were taken simultaneously. With the temperature continuously rising, a series of readings were taken and PV/T calculated. The results were so enocuraging that it was decided to modify the apparatus; the accompanying photograph shows it as finally constructed.

A glass U-tube about 12 inches long was sealed flat (not hemispherical) at one end. A piece of a meter stick was placed behind the arms of the U, and the two were fastened to a wider support. The support was then placed in a wooden box, with a glass front, of dimensions 15x6x7.5 inches. A thermometer can be inserted in a hole in the top of the box, preferably with its bulb about half-way between the top and bottom so that it will indicate the average temperature.

Behind the U-tube support, the heating coil is suspended by heavy copper wire leading to binding posts on the rear of the box. The coil is about 8 inches long and 1/4 inch in diameter, and is made of 24-gauge manganin wire.

For a large laboratory section, several of these pieces of apparatus, preferably of different resistances, so that the rates of heating will be different, can conveniently be connected in series with a single rheostat and ammeter, to a 110V AC main. In practice it has been found advisable to start with a current of about 2.5 amperes and to increase this by steps to about 3.5 amperes. Too rapid heating will cause the thermometer to indicate too low a temperature.

Having the tube filled with dry air is of prime importance in obtaining results that really give a constant value of R, com

puted from PV/T, as can be seen from the accompanying tables of data. Table A refers to a tube containing a high percentage of moisture, B to one containing ordinary room air, and C to one containing dry air. Table C was obtained with a tube that had been heated and evacuated to drive off the occluded gases and filled with air bubbled through concentrated sulphuric acid, the heating, evacuating, and filling being repeated ten times before the mercury was introduced. The tube referring to table B was heated and evacuated and then filled with ordinary room air.

If desired, the apparatus can easily be modified to admit of greater range of pressure change and of volume change. The small cost of construction, the simplicity of design, and the ease of manipulation of this piece of apparatus as well as the importance of the laws it illustrates should recommend it to both the high school and college teacher of physics.

Room Air Dried by Heating and Evacuating Tube

Top of Closed Tube 59.7 cm.

Barometer 76.5 cm.

Northern Illinois State Teachers College, DeKalb, Ill. Physics deals with so many things connected with our home, school and community life, that if it is presented in a practical, rather than the usual cut-and-dried way, it is both interesting and instructive to our youth. Half a century ago there were fewer inventions and up-to-date conveniences, so the people of both city and farm were able to become acquainted with the limited number of things belonging to the field of science. The few conveniences then were learned easily at home, and the people were relatively more efficient than now. But inventions during the last half century have multiplied so rapidly that the home has been unable to keep up with them, so that the burden of making our youth efficient has fallen more and more upon our schools and colleges. Those institutions as a whole are failing in much of this efficiency work.

Listen to some of the adverse criticisms of science teaching that are offered: "School work, especially in science, is too artificial-not real." "Most of the science subject-matter taught remains unused, both in and out of school and college hours and in after school years." "The big problem of the school is that there is very little relationship between the work of the school and the work of the world." "Our physics books are too much on the order of encyclopedias or dictionaries, and their proper function is for reference only." "We lack books for high school and college which present science as living projects." "The basic

error in science teaching today is that it does not center itself about the interests and desires of the students."

One of the professors in Columbia Teachers College asks and answers this question: "Why do we, as mature people, go to the literature of the automobile company to learn about the workings and methods of repairing of our batteries, and to make other repairs, rather than to a physics text book? Simply because the company's literature satisfies us, and explains in a practical, instructional way the workings of the battery and other parts, and touches closely and appealingly to the project we have." "We must remember," he adds, "that students are immature men and womem and do not enjoy studying dry, unrelated facts, principles, theories and fundamentals any more than we would."

Why not bring small samples of real life and real workable problems to the school and college more than we do, and give them as projects, those which will appeal to and grip the students? This will not only interest them and show the worthwhileness of physics, but it will develop their thinking power. Dewey says that "there is no thinking without a problem. When judgment is challenged to face a dilemma it makes a fork in the road and thinking begins here."

I grant you that there are difficulties in the way of teaching by the project method, such as large classes, lack of suitable projects, the time factor in the teacher's and student's busy life, lack of trained teachers, lack of equipment and supplies, etc. Yet many science teachers in high school, normal school and college are doing work of this kind, and our plea now is for many more teachers to tackle the problem and thus give students worth-while opportunities of studying science in practical ways.

Since time for this paper is so limited, I will confine myself to one phase of work in physics, namely, some practical projects in electricity. A few years ago while teaching a small class of high school boys we took up some projects in electric wiring. Several small, roughly boarded rooms in the manual training department served our purpose. Only three sides and ceiling were boarded, leaving the front of each room open. In these rooms the students worked out in detail a number of projects in electric wiring of homes, such as door bells, call bells and lighting. The interest was keen, thinking was stimulated, and the results educationally were good, even though not all of the indvidual work was neat and perfect. At other times practical electric burglar alarms for windows were worked out and some students installed them in

their homes.