Our readers will notice that engravings of this Engine were published in No. 4, Vol. 8, Scientific American. Mr. Barrow's has pursued the subject of Rotary Engines with a great amount of energy for several years, and were such an engine to supersede the kind in use we think there are very few men who would be more likel to succeed than the inventor of this. such the pleasure the other day of taking a short excursion upon the steamboat Rotary Experiment lor the purpose of observing the operation, speed, &c, of this miniature boat. She was built for the purpose of testing the operation of this engine, and is but 70 feet in length. This boat (" Rotary Experiment ") left the Atlantic Wharf at about eleven o'clock ; starting with but a slight head of steam, she gradually began to increase her speed, and passed out into the bay indirectly toward Greenwood, from thence up the North River, ten miles, and was back opposite the Battery at about 1 o'clock, being an average speed of about 10 miles per houi. During a portion of the time. She encountered a heavy north wind and an opposing tide, so that when running with the tide her speed must have exceeded the above rate. We saw no difficulty in keeping her in proper order. The mercury gauge there used, ranging at about 70 lbs.,was very uniform initsheight. This mustbe deemed a good experiment, considering the size of the boat, and is probably ahead of any other ever made. We do not oppose any experiment when there is a possibility of success, though the chances ma.y be doubtful. Our opinions have been often expressed through the Scientific American upon this subject; still, judging from the past, we dare not venture what the future may not bring forth, all that we say is, that this field of invention has been explored and re-explored by men of rare genius and skill, and the result has thus far been a most ungrateful harvest. Another trial trip will come off on Saturday, June 11, for the purpose of further testing the practical operation of this boat. Mr. Barrows believes his Rotary Engine has decided advantages over the Reciprocating and Oscilating Engines, and respectfully solicits a fair investigation of its merits. For that purpose he will run his Steam Yacht Rotary on trial trips, and respectfully invites all practical engineers and scientific gentlemen who feel an interest in steam navigation, to call at his store, No. 228 Water street, corner of Beekman, and register their names, when a ticket will be presented to each, for a trip, and proper information imparted.