Properly graded sieves with meshes of a reliable size are often of great use. They should be made out of proper "bolting" cloth, a beautiful material made for flour-millers. Messrs. Henry Simon and Company of Manchester have kindly furnished me with the following table of materials used in flour-milling. Sieves made of these materials will be found to work much more quickly and satisfactorily than those made from ordinary muslin or wire gauze. Relative Bolting Value of Silk, Wire, and Grit Gauze Threads per inch Trade No. Trade No. Trade No. of Approximate. of Silk. of Wire. Grit Gauze. 18 0000 18 16 22 000 20 20 28 00 26 26 38 0 32 34 48 1 40 44 52 2 45 50 56 3 50 54 60 4 56 58 64 5 60 60 72 6 64 66 80 7 70 70 84 8 80 80 94 9 106 10 114 11 124 12 130 13 139 14 148 15 156 16 163 17 167 18 170 19 173 20 Sec. 145. Pottery making in the Laboratory. When large pieces of earthenware of any special design are required, recourse must be had to a pottery. Small vessels, plates, parts of machines, etc, can often be made in the laboratory in less time than it would take to explain to the potter what is required. For this purpose any good pipeclay may be employed. I have used a white pipe-clay dug up in the laboratory garden with complete success. The clay should be kneaded with water and squeezed through a cloth to separate grit. It is then mixed with its own volume or thereabouts of powdered porcelain evaporating basins, broken basins being kept for this purpose. The smoothness of the resulting earthenware will depend on the fineness to which the porcelain fragments have been reduced. I have found that fragments passing a sieve of sixty threads to the inch run, do very well, though the resulting earthenware is decidedly rough.