DOUGLAS D. SMITH Gullford High School Rocklord, Illinois 6111 1
Wonder Water (?) The following is an excerpt from a letter sent by Dr. W. H. Eherhardt, Georgia Institute of Technology, Atlanta, Georgia. I wonder if you know about "fast water"and "slow water," otherwise known as Der Filtereffekt?T h e phenomenon was called to my attention years ago by a colleague who also pointed out that it was described in the technical literature.' The essence of the experiment is that, if vou pass a mea. . wrrrl ~ m o u nuifluid, i e g., rap water, thruugh n scintiwd-glass ijl~cr,thp ;mmunt d rime i t takes it) pass through rhe filter decreases the more you pass it through. That &if it takes a certain time, like 25 sec, for 100 ml of the water to pass through the filter the first time, it will take only 18 sec to filter it through the second time, and only 16 sec or so the third time. But, if you let this "fast water" stand overnight, it becomes "slow water" again. The experiment is easy to do with a scin-
Pass-Fail versus Conventional Grading Gatta' did some interesting research in regard to Pass-Fail versus Conventional Grading in high school chemistry. As a result of this study, he concluded that students in a pass-fail eradine svstem showed lower achievement and poorer attisystem. Howe: in reviewing tudr..; I lun rhost, in a cu~~ventional this resr;~rrhp
