1.You have heard of volcanoes,and you know that they are openings in the surface of the earth,through which smoke,steam,hot ashes,and melted rock are poured out.From them we know that the inside of the earth is very hot,and quite different in many ways from the outside.
2.It may not seem at first that volcanoes have much to do with slate-pencils,but men who have studied the matter tell us that our slates and slate-pencils really came out of volcanoes.They have changed a great deal since that time,as you will easily believe.
3.Most volcanoes break out near the sea,some of them even underneath it.The melted rock that comes out hardens into a kind of stone called lava.The dust and ashes,however,settle down in the sea,and become fine soft mud,and this is what we have to do with at present.
4.You perhaps know,too,that rivers are constantly carrying down sand and mud,and this also settles on the bottom of the sea.The volcanic ashes are covered over with layer after layer of the sand and mud of the rivers,and in the course of ages they are pressed and hardened into stone or rock.
5.Now the slate-pencil you are using was long ages ago in the form of mud made from the ashes of a volcano,and was hardened by the pressure of rocks that were formed above it out of the river sand.Then it went through a great many changes caused by the action of volcanoes:it got twisted,and set on end,and squeezed,and bent,and broken,until-partly from this treatment,and partly from the great heat inside the earth-it was gradually changed into what we call slate.
6.After all this had happened,the whole of the part of the earth where it lay was raised up somehow above the level of the sea,and those rocks which had been under water so long were made into ranges mountains.
7.If you went to North Wales,you would find the slate-beds there up heaved in all directions.They look as if they had been very badly used in the old days of the volcanoes.But all that is over now,and you would see there thousands of workmen digging and blasting from the quarries the slate which has been made fit for our use in such a strange way.
8.Do you wish to know now how your school slate was made?When slate is taken from the quarry,it is sent to a slate-maker,who splits it into blocks about two inches thick.He does this by driving a wedge into the place where it will split most easily.On account of the heating and the squeezing which the slate has suffered,it splits more evenly and more easily than any other kind of stone.
9.Then a slate-splitter takes slate after slate from each block with the help of a chisel and a mallet ,and a man called a dresser cuts each slate to the right size and makes its edges straight.After this the slates are prepared for writing on by a machine which grinds the surface quite smooth.
10.Slate-pencils are cut in long narrow strips,and then smoothed and rounded,and put into little boxes for sale.They are not made of the best slate.Our British slate would not do for them;it is too hard.There is a softer kind of slate found in Germanyand Austria ,and it is of this soft slate that your slate-pencils are generally made.
