tance to the teachers and research workers as well as the future plant man. In fact, too much cannot be said in favor of this course. Certain summer-school courses in chemical engineering have become of great importance especially to teachers of chemistry. These courses interest the student because they give him an intimate picture of our great modern developments.
Cod-Liver Oil Fails As Egg Stimulator. Cod-liver oil and ultra-violet light do not seem t o have the happy effect on the egg-laying capacity of hens in Great Britain that they have had in America. The value of ultra-violet light in practical poultry farming bas been tried out by Eric W. Mercer and Dr. F. H. W. P. Tozer a t the poultry farm of the Berkshire and Buckinghamshire Joint Sanatorium, which produces about 36,000 eggs every year. The experiments were carried out in winter, hut conditions were planned so as t o allow the hens free access t o open air, sunlight, and grass. The diet was good, with plenty of greens, but the supply of vitamin D was purposely kept low. Six control hens were kept on the basal diet, and four experimental sets (of six hens each) had the basal diet with various additions. In each case, records were made of the number of eggs laid in eleven weeks. The results showed, however, that in each group of experimental hens less eggs were actually laid than hy the controls. From this experiment the investigators concluded that poultry keepers who keep their birds under proper open-air conditions with suitable food and plenty of green stuff will gain no benefit by feeding cod-liver oil or irradiating either the fowls or their feed.-Science Sewice Coating on Vacuum Tube Filament Helps Electrons Escape. How a thin layer of atoms of cesium on the mament helps the vacuum tuhe of a radio set to work better was described to the American Physical Society, recently, by Dr. J. A. Becker of the Bell Telephone Laboratories in New York. Dr. Becker told of work that he had done in collaboration with D. W. Meuller of the same Laboratories. The operation of a radio tube, he explained, depends on the copious emission of electrons from the hot filament. When coated with cesium, in the form of cesium oxide, the atoms of the metal arrange themselves over the filament in a single layer. But the atoms are ionized, which means that each of them has lost one of its quota of electrons and so is positively charged. This atomic layer is then able to act in the same way as the grid of the tuhe, hut being so close t o the filament is particularly efficacious in pulling the electrons out of the tungsten of which it is made.-Science Sencie X-Rays Make Crystals Glow. Another newly discovered effect of x-rays, by which they impart t o certain chemical substances the power of glowing when slightly heated. was described t o the meeting of the American Physical Society,recently, by Dr. Frances G. Wick of Vassar College. Dr. Wick told of work that she had done in collaboration with Miss Mabel K. Slattery, research assistant at Cornell University. Some substances, such as fluorite and calcite, have long been known to possess the property of shining in the dark after being moderately warmed, she stated. However, the investigators have found that chemicals which do not have this power acquire i t when exposed t o x-rays. One of these is calcium sulfate, of which gypsum is a form, mixed with a little magnesium. The phenomenon is called thermoluminescence and is of two kinds, i t was said. One dies out quickly, but with the other, the power t o glow when heated may continue for months.-Science Se-e
