paving blocks but a few inches long, cut across the grain and set on end, are under conditions different from, and probably much more trying than those to which long timbers are ordinarily exposed.

But on the whole, your Commissioners consider this process the best at present available for preserving wood to be used for pavements.

Your Commissioners are of the opinion that if the city adopts any method of preserving blocks to be used for pavements, some additional security should be had that the treatment of the wood shall be thorough and complete.

CONSTRUCTION OF WOOD PAVEMENTS.

For durability under the wear of travel, spruce seems to have few, if any, equals amongst the woods in common use. This, and its moderate cost, make it rather the best material for wood pavements, provided its resistance to decay can be sufficiently increased by preservative treatment.

A firm foundation is indispensable for making a good pavement. To make such a foundation, the earth of which it is composed should be saturated with water and rolled.

Many attempts have been made to overcome or mitigate the bad effects of unequal settlement in foundations,- in other words, to bridge over the depressions, — by the use of flooring under the blocks, also by interlocking the blocks, and by the use of connecting pieces between them. But a flooring one or two inches thick is not stiff enough to carry heavy loads over depressions or cavities of any considerable size, and it is hardly practicable to interlock or connect the blocks strongly enough to do this during any long time. When there are cavities or soft places, the pavement soon cripples down under ordinary use.

Floorings and connections are inconvenient, when, as often happens, it becomes necessary to take up pavements for obtaining access to pipes or sewers.

When portions of a pavement are taken up and excavations are made, it is difficult to refill and restore the pavement so that its surface will remain uniform with that of the adjoining pavement which has not been disturbed.

Your Commissioners do not hesitate to say that a very large portion of the repairs of street pavements is necessitated by the frequent tearing up for obtaining access to water-pipes, gas-pipes, and drains, or for repairs on the same. Too often, the refilling and repaving are improperly done, and the result is a bad depression, or a disagreeable elevation tending to produce a depression on each side.

If a wood pavement is to be laid on an unconsolidated foundation, flooring or connections may retard unequal settlement considerably if the travel is light, and slightly under heavy travel; but they cannot reasonably be expected to keep the pavement in permanent good condition.

Your Commissioners believe that the best method of constructing wood pavements is as follows:

The rows of blocks should be set square across the street, and should be about four inches thick at top, with spaces of about one-half inch between the rows. This may be done with blocks of uniform thickness set apart, or with tapering blocks half an inch thicker at bottom than at top. The latter arrangement is the more costly, but it is believed by some that it will stand better, by reason of it covering the whole surface of the foundation. Longer trial is necessary to settle this point beyond dispute.

Blocks with only a short chamfer at the top leave the inter-space too narrow, as the blocks wear down.

CONSTRUCTION OF STONE PAVEMENTS.

Your Commissioners consider it important to have a firm foundation for a stone pavement. If a foundation settles much, it generally settles unequally.

Your Commissioners recommend granite blocks 4 inches thick and 8 inches high, well fitted and set close together, in rows square across the street, as the best form of stone pavement known to them.

Mr. Whidden understands the order under which this commission is acting, to call for an opinion as to the relative merits of stone and wooden pavements; the other members of the commission do not so construe the order, and hence express no opinion upon this matter.

Mr. Whidden desires to say, that with our present experience and knowledge, wooden pavement must be regarded as one of the luxuries of the age, and should be restricted to particular locations, and guardedly applied until, at least, a more extended practical trial is had.

Its merits seem to be its freedom from noise, its producing less obstruction to the traction of vehicles, and less wear. This is very agreeable and pleasant. To offset this, it is expensive at the start, if properly done, depreciates and decays early, and is entirely lost after a few years.

ESSAYS.

Your Commissioners have received a large number of essays for examination; several of which show evidences of care and study.

By direction of your Commissioners, each essay was accompanied by the writer's name enclosed in a sealed envelope, bearing a motto corresponding to one upon the essay and only the envelope corresponding to the successful, essay has been opened.

Your Commissioners are unanimous in according the premium to the writer of the essay endorsed "Competition," Mr. F. W. Clarke, of Boston.

Respectfully submitted.

J. M. MERRICK, Secretary.
JAMES F. BABCOCK.
THOMAS J. WHIDDEN.
NATHANIEL O. HART.

EDWARD SAWYER.

AN ESSAY UPON THE

PRESERVATION OF WOOD

FROM DECAY,

WITH PARTICULAR REFERENCE TO THE PROTECTION
OF WOOD PAVING.

BY F. W. CLARKE.

THAT the protection of wood from decay is one of the most important of industrial problems can hardly be denied. And yet in this country it has scarcely begun to receive proper attention. Our forests are rapidly wasting away, the price of wood is continually increasing, its applications are becoming more and more numerous, and still little is done. In 1855 lumber sold for about $18 per thousand, in 1860 for $24, and in 1865 for $45. Although a single acre of pine land yields on the average only about six thousand feet of timber, billions of feet are annually sold in the United States. At this rate our forests must soon become exterminated. The question of preservatives will force itself upon our notice so vehemently that it cannot be ignored. Prudence already insists upon a more rigid economy.

In Europe, on the other hand, much attention has been paid to the problem; England, France, and Germany taking the lead. In Great Britain alone not less than fifty patents for the preservation of wood have been taken out during the present century. To be sure, some patents have also been granted at Washington, but their value was slight. What is the consequence of this trans-Atlantic superiority? Simply that railway sleepers, bridge timbers, and telegraph posts