POPULAR MATHEMATICS 193

12. "Making Mathematics Interesting/’ Math. Teacher, Vol. 17, Pp. 404.13. "Mathematical Games," Math. Teacher, Vol. 17, Pp. 422.

XVI. PLAYS1. "A Living Theorem," SCHOOL SCIENCE AND MATHEMATICS, Jan., 1916.2. "Mock Trial of B versus A," SCHOOL SCIENCE AND MATHEMATICS, Oct.,

1918.3. "A Near Tragedy of B versus A," Math. Teacher, Dec. 1929.4. "The Evolution of Numbers," A Historical Drama in Two Acts, Math.

Teacher, Nov., 1928.5. "If" A Play in Two Acts, Math. Teacher, Dec., 1929.6. "Socrates Teaches Math," SCHOOL SCIENCE AND MATHEMATICS, June,

1923.7. "Flatland: A Math. Play," SCHOOL SCIENCE AND MATHEMATICS, Dec.,

1914.8. "Euclid Dramatized," SCHOOL SCIENCE AND MATHEMATICS, April,

1921.9. "A Math’1 Victory," SCHOOL SCIENCE AND MATHEMATICS, June, 1917.

10. "The Math Quest," SCHOOL SCIENCE AND MATHEMATICS, May, 1920.11. "Falling in Love With Plane Geometry," Math. Teacher, Nov., 1927.12. "Geometry Humanized," Math. Teacher, Feb., 1928.13. "A Little Journey to the Land of Math," Math. Teacher, Oct., 1924.14. "Mathesis," Math. Teacher, Dec., 1927.15. "A Number Play in Three Acts," Math. Teacher, Mar., 1924.

STAINLESS STEEL THERMOMETER FOR LABORATORY USEAn entirely new type of laboratory thermometer, provided with a dial-

and-pointer scale encased in stainless steel, mounted on top of an 8-inchstainless steel stem, is being introduced by the Weston Electrical Instru-ment Corporation, Newark, N. J.The unit is said to be the first dial-type thermometer with an all-metal

temperature element sufficiently accurate for scientific use. The pointeris actuated by means of an internally balanced double coil of thermostaticbimetal sealed in the lower 1-^ inches of the seamless stem. When the stemis immersed to a depth of 1-^ inches in a liquid (3 inches in gas or vapor),the dial reads temperature values accurately without the necessity forstem correction.Accuracy of the unit is guaranteed to ^ of 1% over the entire scale.

In practice, the location of the dial at the top of the stem, removed fromthe liquids or vapors under measurement, encourages a further increasein the accuracy with which readings are made. Dial markings are spacedfor maximum readability on the metal scale plate, and are not subjectedto obliteration from the solutions under test, as is the case with stemgradations. The low temperature values are not obscured in dark-coloredor viscous solutions.The stem of the unit which encloses the temperature element is i-inch

diameter high-strength seamless tubing of "18-8" chromium-nickel alloysteel. It is extremely rugged and completely corrosion-proof to all but avery few laboratory reagents. Construction of the temperature-sensitivecoil is also inherently rugged and shock-proof. Reasonable overrangetemperatures will not affect the accuracy of the unit.

Initial models of the unit are being offered in the following scale ranges:0-220°F., 50-300°F., 50-500°F., 0-100°C., 0-150°C. Applications includetemperature measurement in educational and industrial research labora-tories, in control laboratories, hospitals and general scientific use.