It is kept covered, for purposes of preservation, by a layer of earth.
To comprehend the real position we are forced to the conviction that the world of facts is the field in which, and that laws are the means by which, those higher standards of moral and aesthetical value are being realized; and such a union can again only become intelligible through the idea of a personal Deity, who in the creation and preservation of a world has voluntarily chosen certain forms and laws, through the natural operation of which the ends of His work are gained.
It is only necessary to bear in mind the great part played by sterilization in the laboratory, and pasteurization on the fermentation industries and in the preservation of food materials.
Owing to the fact that the site is largely covered with sand and to the absence of any later alterations, the preservation of the buildings excavated is very good, and Ostia is, - with the exception of Pompeii, the best example in Italy of a town of the Roman period.
There are valuable forests in the mountainous districts, a part of which has been set aside for preservation under the name of the Luquillo forest reserve.