NEW YORK PHYSICS CLUB 159

and in the grades, Supervising Principal Paul G. W. Keller of Manitowoc,Wis., who is producing results in the way of added interest and powerin the study of algebra, Mr. G. A. Harper at the New Trier TownshipHigh School, Wilmette, 111., who is enthusiastic over the problem point

of view in algebra as against mere abstract manipulation, and Mr. J.H. Dickey at the Academy of James Millikin University, Deeatur, 111.,who is a strong advocate of reform along the lines mentioned aboveand is getting results to justify his ideas.The papers are printed in full in the February number of the

Shcool Review, which is devoted to a complete discussion of the con-ference in all departments.

H. E. SLAUGHT, Chairman.

NEW YORK PHYSICS CLUB.The forty-third regular meeting of the club was held in the Erasmus

Hall High School, Brooklyn, on Saturday, November 23, 1907. About40 memb-ers were present. The members were shown the laboratoriesand other equipment of the school and were interested in a wirelesstelegraph station which had been installed by pupils of the school. Apractical test of this station was furnished during the day when amessage was handed to President Woodhull which had been receivedby the wireless outfit. This message was an invitation to Mr. Woodhullto visit and inspect another wireless outfit which had been installedin another part of Brooklyn by pupils of another school.The members listened to an address of welcome by Dr. W. B. Gunni-

son, Principal of the Erasmus Hall High School, in which he spoke ofthe school as the oldest secondary school in New York state; of thepride they felt in the original building, still standing and used for schoolpurposes. Among the early patrons of the school were AlexanderHamilton and Aaron Burr.By means of a lantern and by other experiments, Mr. R. H. Burnham

demonstrated Rayleighs’ principle of reciprocal deflection. This wasdone as follows: two points were taken equidistant from the ends ofa uniform glass rod, and at one of these points a weight was hung.The deflections of both points (magnified) were then noted on thescreen. The weight was then transferred to the other point on theglass rod and the deflections again noted. The deflections were justreversed to what they were before. An irregular glass rod was thentaken and the weight hung near one end as before. Then the weight wasput in the reciprocal position and the deflection noted. They wereagain reversed. The same principle was shown by hanging a weightat different points of a vertical spring.Mr. F. W. Huntington explained and demonstrated Stoke’s principle

of dynamic similarity. This principle may be stated thus: two elasticbodies of similar shape whose linear dimensions are as 1:2 will vibratein periods which are as 1:2. This was illustrated by (1) two bottles,(2) two brass rods, (3) two stretched wires, and (4) two coiled verticalsprings. In all cases the linear dimensions were as 1:2, thus makingthe volumes 1:8. In ’the first three cases the vibratory periods were

160 SCHOOL SCIENCE AND MATHEMATICS

compared by observing the relative pitch obtained from each object com-pared when sounded together. This was done by blowing over the

mouths of the two bottles, by striking the brass rods with a piece of

metal, and by plucking the stretched wires. In all these cases the tonesproduced were an octave apart. In the last case the rate of vibratory

motion was directly observed and the periods were as 1:2.

Mr. H. S. Curtis gave a short talk on the teaching of some parts of

light. He advocated the use of a piece of plane glass, e. g., a lantern

slide cover glass with a piece of dark paper for a background, in place

of a plane mirror with silvered back in the exercises where a planemirror was used; also that a stiff piece of cardboard with very narrowslits held vertically in the path of a sunbeam could be used to showthe path of a ray to individual pupils in the laboratory when usedin connection with a plane mirror to reflect the rays. The path ofa refracted ray can be shown in the same way by making a somewhatwider slit and using a prism. A curved cylindrical mirror in the pathof the refracted beam shows the recombination of the dispersed beaminto white light.Mr. E. L. Von Nardroff delivered a lecture illustrated by many

experiments on the Physics of Sand. He considered first the conditionsthat must exist to’ produce normal piling. This is actually found incannon balls regularly piled. The normal condition of a ball in aregular pile is found when each ball in the pile is touched by 12 others.Sea shore sand is round and approaches the typical spherical formthe more rubbing it gets. The difference between normal piling andloose piling can be shown by placing a liter of sand in a graduatethen gently tapping the cylinder containing the sand for some minuteswhen the sand was found to occupy 890 c. c. When the graduate wasinverted with the hand held over the top to prevent the sand fromrunning out and then reinverted to its usual position, the sand againoccupied 1 liter. Other experiments showed the angle of slope in aloose pile; the angle of slope in a normal pile; the coefficient of friction.Many ingenious experiments were shown to illustrate the transmissionof pressure by sand; the behavior of sand when partly filled withwater; its mobility when wet and normally piled and when dry; its rateof flow. It is hoped that this lecture, together with the other demon-strations, will be published in full in SCHOOL SCIENCE AND MATHEMATICS.

R. H. CORNISH.

ASSOCIATION OF OHIO TEACHERS OF MATHEMATICS ANDSCIENCE.

The Association held its fifth annual meeting in Chemical Hall, OhioState University, Columbus, 0., December 26 and 27, 1907. The at-tendance was the ’largest in the history of tlie Association and overforty new names were added to the membership roll. President J. A.Culler, Miami University, Oxford, presided over the science section,and Vice-President M. E. Graber, Heidelberg University, Tiffin, hadcharge of the mathematics section.The following program was carried out: