1.It has been well said that "in nature there is nothing useless，nothing wasted，nothing destroyed."Everything has its use，although it may be hard for us to find out what that use is.When anything seems to be lost，it is merely changed into something else，and by-and-by we may find out what has become of it.
2.Trees and plants which grew long，long ago in dense forests have been preserved form.When they fell and decayed to us in another and were covered up by water and mud and sand，it seemed as if they were lost，but now we have found them in their new form.They have become coal，and they supply us with light and heat.
3.We are not so clever as nature in finding a use for everything.We pile up useless rubbish in huge heaps on the face of the earth，or throw it down into the sea.
Nature will make some use by-and-by of our refuse ，and perhaps a good use too.We are slowly learning nature's lesson，and in our manufactures we now make use of many things which were formerly thrown away.
4.For a long time the rags of our worn-out clothing were thought to be useless；but at length it was found out that linen and cotton rags could be made into paper.Then these rags were no longer wasted，but were carefully gathered up and used.
5.Even when the paper has been used，it is still not worthless.Waste paper can be cleaned and made in to pulp，and once more turned into paper.Or the pulp made of this waste paper can be pressed into moulds and formed into many things-such as boxes，trays，and toys of various kinds.This pressed pulp makes a very light and strong material，which is now used for telegraph posts and wheels for railway carriages.We call it by its French name，papier-moché.
6.It was found，after some time，that woollen rags could also be made use of.By means of a machine with sharp teeth，they were torn into very small pieces，almost like the wool from which they were spun.Then this wool was once more made into a cheap kind of cloth called shoddy，or it was mixed with new wool and woven into ordinary cloth.A large trade in shoddy is carried on at Dews bury in Yorkshire.
7.Broken glass does not seem of much value，but it also has its uses.It is sometimes mixed with fresh material，and then melted down to form new glass.But there is another use for it.It is ground down very fine，and then mixed with glue，and spread over sheets of paper.This forms the sand-paper or glass-paper which cabinet-makers use for polishing wood.
8.Coal-tar is a black，sticky substance which comes from the coal we use in making gas.Forty years ago it was worth very little；a gallon of it could be got for a halfpenny.Its chief use was to paint the bottoms of wooden ships and boats，to keep them from rotting.But in the year 1856 it was discovered that a beautiful purple dye could be made from it.
Now we can produce all the colours of the rainbow from this black coal-tar.
9.From the same dirty-looking substance we can get a white powder which can be used instead of sugar.It is very much sweeter than sugar，however-about three hundred times sweeter，when pure.Think of a lump of sugar strong enough to sweeten three hundred cups of tea！This substance is said to have been discovered accidentally by a chemist who was working with coal-tar，and who sat down to dinner without having washed his hands carefully enough.Everything he ate tasted so sweet that he was led to look more closely into the nature of the substance with which he had been working.
10.From coal-tar also we now get various kinds of oil，and even some things that are of great value as medicine.Thus we are learning，little by little，to follow nature's plan，and to find a use for everything.And if we learn from the past，we shall call nothing worthless.Who can tell but that a few years hence things that we now think useless will be found to be of the greatest value？