Table No. 41 shows the composition of the ingredients to be used in the manufacture of Portland cement in Kentucky.

Table No. 42 shows the domestic production in barrels, and the imports of Portland cements, for comparison.

TABLE NO. 42.

1890. 1891. 1893.

1894.

1895. 1896. 1897.

1898.

335,500 454,813 590,652 798.757 990.324 1.543,023 2,677,775 3,692,284 1,900,000 2,988,313 2,674,149 2,638,107 2,997,395 2,989,597 2,090,924 2,013,818 2,235,500 3,443,126 3,264,801 3,436,864 3,988,719 4,532,620 4,768,699 5,706,102 85,486 53,466 36,732 4,447,134 4,715,233 5,669,370

It can readily be seen how strong a hold American Portlands have on the market, when from 1896 to 1898 the imports fell off 975,719 barrels and the domestic production increased 2,149,261 barrels. The value of the domestic product for 1898 was $5,970,773, or about $1.62 per barrel.

Table No. 43 shows the amount of American natural cement produced from 1893 to 1898 inclusive, and also the consumption of all kinds of cement for the same time in barrels.

A barrel is assumed to contain 300 pounds of natural or 380 pounds of Portland cement.

The total value of the natural product for 1898 was $3,888,728, or $0.46 per barrel.

CHAPTER VI.

THE THEORY OF PAVEMENTS.

LORD MACAULAY said in his History of England: "Of all inventions, the alphabet and printing-press alone excepted, those inventions which abridge distance have done most for the civilization of our species."

Adam Smith once asserted that "the construction of roads is the greatest of all improvements." While these remarks had special reference to communication between towns or villages, they can with equal force be applied to cities and towns themselves. Some one has said: "Tell me the condition of the churches of a city, and I will tell you of the prosperity of that city." If this be true of churches, how much more truly can it be said of the pavements! Probably no one condition in a city strikes a stranger as forcibly as the general appearance of its streets. The clean and improved pavements of New York City during the last few years have impressed the rural visitor more than any one other feature of the city, the tall office-buildings, even, not excepted.

The word "pavement" comes from the Latin pavimentum and means "a floor rammed or beaten down"; hence the hard smooth surface of a street can be called pavement. It can be defined as the artificial surface of an improved roadway formed of hard or durable material for the purpose of facilitating travel and forming a presentable surface to a street at all seasons of the year.

There has been considerable discussion among engineers as to what really constitutes a pavement. Its importance can be seen when it is remembered that a great many cities compel abutting property owners to pay for the first pavement, but keep it in repair and renew it at the expense of the city at large. The people, knowing this, often make their first improvement as cheaply as possible,

leaving to the general public the task of effecting a real and permanent improvement.

Pavements have been laid of many materials, both perishable and imperishable, natural and artificial. The experience of one city has not seemed to benefit very greatly any other, but it has seemed necessary for each one to work out the problem for itself. This was especially true in earlier years, when there was less communication between city officials and when, too, there was less interest taken in the subject. At the present time the ideas of city officers are spread abroad through the medium of official reports, technical societies, and technical journals, so that one can easily know what is being done in outside cities by keeping in touch with these means of communication.

But it by no means follows that the decision as to what is the best paving material for one locality will necessarily govern in another, however intelligently it may have been reached. There are so many conditions affecting this question that it must generally be decided by their careful study in each particular case. For instance, stone may from its proximity and availability be just the material for one city and the cost of transportation make it prohibitive for another, and some other material must be used.

The value of pavements to a city or a particular neighborhood is positive and immediate. Real-estate owners, than whom no more shrewd or sagacious men are in business, recognize this, and when they wish to put a piece of property on the market at once and at good prices, always pave the streets with the most popular material. The pavement improves the appearance of the streets so much that the lots not only sell more rapidly, but the owner can add to his price more than enough to reimburse him for his outlay.

Of how much importance street pavements are in a large city can be understood only by a knowledge of their cost and extent. In the present city of New York there were 1720 miles of pavements on January 1, 1900. Assuming the cost of a good pavement to be $2.25 per yard and the average width of a street to be 30 feet between curbs, the cost per mile, including curbing, will be about $50,000, making a total of $86,000,000 New York City would have invested if her street pavements were all of good character and in good condition. Or assuming that each street must be repaved

every twenty-five years, to keep the above mileage renewed when worn out will require the laying of 69 miles of street pavement each year. Assuming further that the average cost of repairs to all pavements will be nothing for the first five years, and three cents per yard for the remainder of its life, the total annual expense for maintenance and repairs on the present mileage of New York City's pavements will be $528 per mile, or $690,096 for repairs and $3,450,000 for renewals, or a sum total of $4,140,096 per annum to keep the present paved streets of New York in good condition. Other cities will have less cost, but this illustration shows the necessity of careful study and investigation.

It will be of interest and value to know how these vast sums are raised; and while payments for all public improvements must come from the property owner, the methods of obtaining it vary much in their detail.

In a paper called "Theory and Practice of Special Assessments" read before the American Society of Civil Engineers by Mr. J. L. Van Ornum, the methods of paying for street improvements in fifty cities were given. Table No. 44 is compiled from this paper.

When special assessments are made against the abutting property different methods are adopted for payments. In certain sections of the West the tax is due in instalments, special bonds being issued to raise funds to pay the contractor, which bonds mature as the instalments are paid, and are not considered as a general indebtedness against the city.

In other places the entire amount is payable when the work is completed, tax certificates against the property being issued to the contractor as payment, and he being compelled to make all collections. In the East it is more common to make the tax payable after work is completed and assessment laid, funds being provided temporarily by the issue of stock of the city.

When the amount of money involved is so great, it is not strange that many inventors have been at work and many experiments made to determine what is the best material for pavements. As a result streets have been paved with stone in varied forms and shapes, wood, asphalt, coal-tar, cement concrete, iron, brick, india-rubber, shells, gravel, slag blocks, and even glass and hay; and many of