With an Atlas strength of mind Prof. Porter has labored for the past seven years to bring into practical operation a perfect system of aerial navigation. Many pilgrimages has he made, and many difficulties has he met and vanquished in pursuit of this grand object.— Although often discouraged he would never give it up so, but on he went with eye un-quenched by the sunshine of prosperity, or -dimmed by the clouds of adversity, towards the grand object of his desires. Hie ambition to soar has been like that of the eagle, proud bird of the sky. He labored some years in New York City, in order to bring his wonderful balloon, named the Revoloidal Spindle into public notice, and along with Mr. Rob-john, astonished our citizens in the Tabernacle one evening in 1849, by making a model of it sail through that building as graceful as a whale. One of these aerial machines was to start from New York for California in April 1849, but somehow or other, instead of getting up it always got down, and Prof. P., disgusted, we suppose, at the ingratitude or blindness of the New Yorkers, to the merits of his machine, pulled up stakes here, and pitched his tent in the metropolis—Washington. Since he has made that city his place of abode, we understand he has devoted himself t o his great work—aerial navigation—with a constancy of purpose, and a zeal which should arrest the attention of all high-flyers. We now learn by the Washington papers that Prof. P. has again given occular demonstration of the practicability of aerial navigation, by the exhibition of an operating aeroport, 23 feet long, and furnished with a steam engine and a pair of propelling wheels, whereby the apparatus is propelled rapidly through the air in any required direction. The exhibition is favorably spoken of as being highly exciting and gratifying to those who witnessed it. Last year he commenced the construction of an aeroport or flying-ship, 160 feet in length, and nearly completed it before the approach of winter compelle3**fiim* to suspend operations. When this is finished he intends to construct another of much larger dimensions, and capable of carrying passengers at a speed of 100 miles per hour, the practicability of which he apparently demonstrates as clear as mud in his lectures, and in a small pamphlet, in which the principles and construction of the machine, and the mode of managing the same, are described; and he moreover contends and demonstrates that this mode of traveling will be much more safe than by railroads or steam vessels. This large aeroport is estimated to cost $15,000, and is to be owned in shares of $5 each. About six hundred of these shares (amounting to $3,000) it is said, have been taken and the money paid in, and, in order to secure the shareholders from any liabilities ot assessments, or any responsibilities, Mr. Porter gives for each $5 a regular title deed, which entitles the holder thereof to draw a proportionate share'of the profits that may accrue from said aeroport, payable quarterly. Thus the security of stockholders, namely a certificate of $5 for each share is certainly an excellent plan of securing the issuers ot stock against loss, but it does not clearly appear to us how it secures the purchasers of it. Nevertheless, the project is so grand and vast, it is enough to make mount Vesuvius burst out in fiery laughter. As of yore, Prof. P. has not yet given up the idea of traveling to California at the rate of 100 miles per hour, scaring the grizz ly bear, and startling the deer on the Rocky Mountains. It is his intention when he builds his large aeroport, to run to California from Baltimore in 30 hours, and make two trips per week, carrying S00 passengers each trip. Won't there be great times then. When this wonderful aeroport of the professor is completed, light and intelligence will be diffused among the darkened nations; cannons will be sold for old iron, steamships for coal scuttles, and railway cars for cow pens. There are 6,691 miles of railway in England, from which'- . 44,8 of receipts per mile hae been obtained during the last quarter.