Soil mechanics necessary to run water through the sieves to wash the coarse particles and clods through. A variety of sieve sizes are available. The boundary between sand and silt is arbitrary. According to the Unified Soil Classification System, a #4 sieve (4 openings per inch) having 4.75mm opening size separates sand from gravel and a #200 sieve with an 0.075 mm opening separates sand from silt and clay. According to the British standard, 0.063 mm is the boundary between sand and silt, and 2 mm is the boundary between sand and gravel. The classification of fine-grained soils, i.e., soils that are
Granular dogfish Granular dogfish The granular dogfish, "Centroscyllium granulatum", is a little-known, very small dogfish shark of the family Etmopteridae, endemic to the Falkland Islands. The granular dogfish has no anal fin, two dorsal spines with the second one much larger than the first, a large second dorsal fin, a long abdomen, small pectoral and pelvic fins, a large eye, prominent nostrils and spiracles, and brownish-black coloration. It is very small, growing to only 28 cm. They have only been found around the Falkland Islands in the South Atlantic. Almost nothing is known about this shark. It has been caught at around