Show 1 V how school slates are made slate Is a variety of rock having a small compact grain and a very fine continuous cleavage or r splitting structure by which it 16 can be he separated into thin even plates of great consistency it was orgin originally ally just so much soft oft tit mud ud on the floor of an ancient sea but in the course of ages it became consolidated and then metamorphosed r or gradually altered in tit character by the continued operation of various ciatu natural forces until its present condition was attained tiie the chief employment of slate in commerce is that of a roofing material for which purpose it is better adapted than any other substance that has yet been tried school slates are prepared in a very si simple manner from picked specimens of t the h e common roofing variety those of the welsh quarries however being generally pre feared to any other the plates which are to be made into writing slates must have a homogeneous or finely grained and equal texture and be without any yellow pyrites or slate diamonds as these familiar glittering crystals are often termed after they have been separated from the 0 other ther sorts they are carried to workmen who fashion them into school slates by first splitting them up tip evenly if required and then finely polishing them over with specially adapted steel tools they are next sent to the joiners to be fitted with wooden frames after which they are quite ready really for the educational markets at home or abroad yankee blade |