The contribution of handwriting to learning to write was examined in an experimental training study involving beginning writers with and without an identified disability. First-grade children experiencing handwriting and writing difficulties participated in 27 fifteen-min sessions designed to improve the accuracy and fluency of their handwriting. In comparison to their peers in a contact control condition receiving instruction in phonological awareness, students in the handwriting condition made greater gains in handwriting as well as compositional fluency immediately following instruction and 6 months later, The effects of instruction were similar for students with and without an identified disability. These findings indicate that handwriting is causally related to writing and that explicit and supplemental handwriting instruction is an important element in preventing writing difficulties in the primary grades.Horace Greeley, the founder of the New Yorker, often wrote notes and letters that were difficult to decipher. After writing a letter indicating that he would be unavailable to make a solicited presentation, he received a reply, noting that it took some time to translate his response, but that his requested date, terms, and honorarium were acceptable (Hendrickson, 1994).Unfortunately, misinterpretations are not the only consequence of handwriting difficulties. For children, there are at least three additional unwanted results. First, poor penmanship may influence perceptions about a child's competence as a writer. When teachers or other adults are asked to evaluate two or more versions of a paper differing only in handwriting quality, neatly written papers are assigned higher marks for writing quality than papers of poorer legibiUty (e.g.

Measurements of the thickness of the pre-corneal tear film, pre-lens tear film, post-lens tear film, and the lipid layer on the surface of the tear film are summarized. Spatial and temporal variations in tear film thickness are described. Theoretical predictions of tear film thickness are discussed. Mechanisms involved in the upward drift of the tear film after a blink, and in the formation of dry spots, are considered.

Evaporation in our "free-air" conditions may be four to five times faster than the average of the values reported in the literature when air currents are prevented by preocular chambers. However, recent evaporation measurements using "ventilated chambers" give higher values, which may correspond better to free-air conditions. Thus evaporation may be fast enough to explain many cases of tear film break-up, and to give rise to considerable increases in the local osmolarity of the tear film between blinks.

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Analysis indicated that the observed movement of the lipid layer was too slow to explain the observed thinning rate of the tear film. In the Appendix, it is shown that flow under a stationary lipid layer cannot explain the observed thinning rate. It is concluded that most of the observed tear thinning between blinks is due to evaporation.

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