steam stood idle, and every glass of water drunk was carefully reckoned.  Thousands of gallons of water were brought in tanks from neighboring cities, and were emptied into the empty reservoir from whence it trickled slowly through the city mains.  The lack of water caused not only personal inconvenience and business paralysis, but it occasioned real danger of disease through unflushed sewers and insufficiently drained pipes.

The conservation of the forest means the conservation of our waterways, whether these be used for transportation or as sources of drinking water.

CHAPTER XX

MAN’S CONQUEST OF SUBSTANCES

201.  Chemistry.  Man’s mechanical inventions have been equaled by his chemical researches and discoveries, and by the application he has made of his new knowledge.

The plain cotton frock of our grandmothers had its death knell sounded a few years ago, when John Mercer showed that cotton fabrics soaked in caustic soda assumed under certain conditions a silky sheen, and when dyed took on beautiful and varied hues.  The demonstration of this simple fact laid the foundation for the manufacture of a vast variety of attractive dress materials known as mercerized cotton.

Possibly no industry has been more affected by chemical discovery than that of dyeing.  Those of us who have seen the old masterpieces in painting, or reproductions of them, know the softness, the mellowness, the richness of tints employed by the old masters.  But if we look for the brilliancy and variety of color seen in our own day, the search will be fruitless, because these were unknown until a half century ago.  Up to that time, dyes were few in number and were extracted solely from plants, principally from the indigo and madder plants.  But about the year 1856 it was discovered that dyes in much greater variety and in purer form could be obtained from coal tar.  This chemical production of dyes has now largely supplanted the original method, and the industry has grown so rapidly that a single firm produced in one year from coal tar a quantity of indigo dye which under the natural process of plant extraction would have required a quarter million acres of indigo plant.

The abundance and cheapness of newspapers, coarse wrapping papers, etc., is due to the fact that man has learned to substitute wood for rags in the manufacture of paper.  Investigation brought out the fact that wood contained the substance which made rags valuable for paper making.  Since the supply of rags was far less than the demand, the problem of the extraction from wood of the paper-forming substance was a vital one.  From repeated trials, it was found that caustic soda when heated with wood chips destroyed everything in the wood except the desired substance, cellulose; this could be removed, bleached, dried, and pressed into paper.  The substitution of wood for rags has made possible the daily issue of newspapers, for the making of which sufficient material would not otherwise have been available.  When we reflect that a daily paper of wide circulation consumes ten acres of wood lot per day, we see that all the rags in the world would be inadequate to meet this demand alone, to say nothing of periodicals, books, tissue paper, etc.