As a race they greatly excel us in mechanical engineering. Many evidences of their skill might be given, but we will be content to give a description of their monumental engineering feat. Long ages ago Holen had cooled to the center, and it became the ruling passion of her most intelligent inhabitants to communicate from one side of the globe to the other through an opening of five hundred miles almost directly through the center of their earth, or more accurately speaking, through the center of gravity. After forty-five hundred years of experimenting the marvelous feat was accomplished. Of all the worlds in the constellation of Orion, large or small, Holen is the only one that has succeeded in this astounding feat, although it has been and is being tried on more than a dozen worlds. This wonderful opening through Holen's center of gravity is lined with sections of ribbed metal which cost the governments fabulous sums. This vast tube was finished thirteen hundred years ago according to our time. Many lives were sacrificed in the hazardous work of tunneling. Were it not for the ribbed metal which afforded protection with its shelving flanges, the tube could never have been finished. At the present time the tube is used for commercial purposes and for passenger traffic. Air tight cars of special design are used, and only one car is allowed in the tube at one time. [Illustration: The Gravity-Car of Holen.] You cannot imagine the frightful velocity of the ride, but the passenger is not as conscious of this as you might think. The first fifty miles of the descent is controlled by the exterior or surface engines. The speed is gradually increased until it reaches that of the falling body. Then the motorman releases the wizard car and the speed is steady and terrible until the car dashes past the center of gravity, after which the speed slackens at a regular rate. The car of its own momentum forces its way far toward the opposite surface of their earth. Just as the carriage comes to a stop, the engineer or motorman, as we would call him, pulls his lever, thereby fastening the car to the ribbed side of the tube. At once a signal is given and the long, thin but strong rope descends to draw the carriage to the surface. A perfect system of communication is established from one end of the ponderous tube to the other. It frequently happens when an attempt is made to fasten the car that the clamps fail to work and consequently the carriage commences its second journey toward the center. Another effort is made to hold the carriage when it again comes to a stop; but if this is not successful, then comes the most peculiar experience of all. The carriage of its own momentum continues dashing backward and forward until it comes to rest at the center of gravity. Then the engineer, by communicating with the surface, gets the longest stretch of rope and is drawn two hundred and fifty miles to the surface.