The Baton Rouge Gazette, under the above heading, has the following: "William St. Martin, of this city, has invented an engine, which can be constructed, boiler and all, for about $50. The machine is so simple that we might with propriety say it is merely an escape-pipe, taking up no more room. The steam is admitted into the center of a drum or cylinder, in which the shaft works; from this the power is applied directly, without further friction. The other day we saw the perfected model of the engine pump- ing water about twenty fcet, and throwing it into the reservoir at the brewery. This is the apparatus wanted, for getting, in a cheap manner, one or more horse power to drive small machinery. Mr. St. Martin has made application for Letters Patent, and when he gets them, we think he has a fair prospect to realize something from the result of his genins." [The above paragraph has been " going the rounds" of the papers for some time past. The readers of the Scientific American will recognize in this "greatest steam invention yet," simply a rotary engine.Eds.