The Gritted Fly-Paper: Sand That Keeps the Sheets Apart

"The objects of the invention are to prevent the sticky material from spreading or running over the clean margin and onto the back of the sheets while the paper is kept in stock; also, to keep the sticky material evenly distributed on the sheet while it is kept in stock." "We may use small seeds, ground emery, fragments of any kind of hard resin, or coarse sand; or any kind of hard material not soluble in sticky material, or only slightly so, will serve the purpose". "For the purpose of shipping, there are from twenty-five to fifty sheets of fly-paper packed in a box. A considerable pressure is borne by the lower sheets, but if the proper-sized particles exist on the inner surface of the paper the pressure will fall entirely on them, and thus relieve the sticky material altogether".

Make the strips as in the program. Stack the sanded ones in one pile and the plain ones in another, face to face, and put the same weight on each. After a day and again after a week, peel the piles apart. Note which peel clean, which tear, and how far the sticky has crept onto the margins. Hang one strip of each where flies gather and count the catch.

**Otto Thum** and **William Thum** of Grand Rapids, Michigan, filed US 414,606 on 16 May 1889; it is dated 5 November 1889. **Honest limits.** Stefan's law is for a round, flat, even layer of a simple liquid; real sticky coats are neither round nor simple liquids, and the edges of a stack do not all carry the same weight. Viscosity and sizes are examples. What peels clean is the measurement.