DEPARTMENT OF PHYSICS. REPORT BY PROFESSOR G. F. HULL
In discussing the topic : The First Year's Course in Physics, (a) should an attempt be made to teach all parts of the subject, (b) the best order of topics, Principal C. C. Ferguson of Somersworth, N. H., pointed out the difficulty of dealing, even in a very elementary way, with the whole subject in one year and suggested that the less important part should be omitted in the first year and attention directed towards the more general principles and their applications. Mr. L. D. Higgins of the Normal School, Danbury, Conn., strongly favored the plan of making the first year course one for arousing interest in the subject, in training the powers of observation and of reasoning, and not for the accumulation by the student of facts and details. This course should be followed by another year course in text-book and laboratory work.
Mr. C. H. Andrews of the South High School, Worcester, Mass., in discussing the nature of laboratory work deprecated the inclusion in some courses of experiments involving measurement for measurement'ssake. If an experiment did not answer the test of illustrating clearly a physical principle it ought to be discarded.
Professor Gilbert outlined the methods used in Dartmouth College in conducting large laboratory classes in physics. He emphasized the importance of business-like methods on the part of the instructor as well as the student. The system of note-books and report sheets devised by Professor Gilbert has been adopted by the Department of Public Instruction in the new State Science Curriculum which was reported upon by Principal W. O. Smith, of Lancaster, N. H.
On the topic: In what way should entrance requirements in Physics be modified? Principal F. E. Heald of Hanover showed that the present value placed upon entrance physics was only one point in twenty-one, and urged that either a larger credit should be given for a more extended course, or that the subject be dropped from the list of entrance subjects.
Concerning the relation of College Physics to entrance requirements Professor Hull drew attention to the necessity in every college for a course in physics which should be broad without being superficial, which should have a good foundation in mechanics, which should give to the students a clear notion of theoretical and commercial units, an appreciation of precision in measurement, a knowledge of fundamental laws, a power to apply those laws to affairs of everyday life and which should finally make a contribution to the student's appreciation of history and evolution. These are the objects of courses 1 and 2 in the College. It is seldom that a student comes from a secondary school course with a training in physics sufficient for him, if he wishes to take physics in the College, to claim credit for these elementary college courses. In laboratory work on the other hand, if a student presents a good laboratory note-book for work done in the secondary school, he will be assigned to more advanced experiments than are ordinarily given to those not presenting physics for entrance.
Mr. N. Henry Black of the Roxbury Latin School advocated the offering by the College of a short general course, not open to students presenting physics for entrance, to be followed by a more extended general course. This plan has been under advisement in the College, but is at present impossible on account of an inadequate teaching force.
In answer to the question: Should there be a state certification for teachers of physics? Professor Hull urged that some form of certification is wanted to ensure that teachers of physics have had a reasonable training in the use of apparatus in a well equipped laboratory. The Superintendent of Public Instruction, H. C. Morrison, gave a resume of the efforts to bring about state certification of all teachers in New Hampshire.
THE ELECTRON THEORY OF MATTER
Starting with the Greeks the lecturer briefly traced the history of the discussion regarding the structure of matter, quoting Aristotle and Kaub in favor of the notion of continuity or infinite divisibility, and Democritus and John Dalton in favor of structure or indivisible particles. The last named scientist one hundred years ago practically established as far as chemistry is concerned, the atomic theory of matter when he discovered the "law of multiple proportions."
Turning to the domain of electricity the speaker showed that the so called positive and negative electricities differ from each other in the way in which they are associated with matter. This difference is especially brought out when an electric current passes through a salt solution or through acidulated water. There it is seen that hydrogen atoms are always positively and oxygen always negatively charged. Moreover, the amount of electricity carried by a hydrogen atom is always a constant. This small quantity of electricity is evidently the smallest amount experimentally obtainable. We might call it the atom of electricity.
But when an electric current passes through any rarefied gas it is found that a negative atom of electricity is carried by a particle having a mass only about one seven-hundredth of that of a hydrogen atom. These negatively electrified corpuscles or electrons form the so called cathode rays—discovered by Sir William Crookes over thirty years ago. Only recently, however, through the experiments of J. J. Thomson and others, have we become acquainted with their most important characteristics.
Experiments were shown demonstrating the deflection of these cathode rays by means of a magnet. By measuring the amount of this deflection and the corresponding one produced by an electrical field the mass of the particle and its great velocity-that of one hundred thousand miles per second—can be determined.
The difference between positive and negative electricity is again brought out by the fact that we never find positive electricity associated with so small a mass as that of an electron. A hydrogen atom is the smallest mass positively charged. From experiments now under way it looks as though positive electricity is generally carried by particles of this size whatever be the nature of the rarefied gas through which the discharge takes place—a result which may clear up our ideas regarding the relation between matter and electricity.
The lecturer showed by means of positive streams in hydrogen, helium and mercury vapor that the positive carriers are not easily deflected by a magnet and gave the argument for believing that they are large compared with cathode corpuscles.
The existence of positive and negatively charged particles in the vicinity of a bunsen flame, a nerust lamp filament and radium was shown by their action in discharging an electroscope.
Turning to a more speculative field the lecturer gave an account of the attempt on the part of J. J. Thomson to explain the periodic law of the elements by supposing an atom to be composed of electrons in a sphere of postive electricity. This was illustrated experimentally by the way in which magnetised needles, floated vertically by small corks 011 the surface of water, arranged themselves.
This electron hypothesis may also be used to account for the definite arrangement of the spectral lines giVen out by a luminous gas. To illustrate this arrangement the spectra of mercury vapor and of argon, when small and heavy electric discharges passed through it, were shown.
