A mechanic in Rochester has invented an atmospheric hammer, intended to displace the trip and tilt hammers. The principle applied to move the implement is not unlike that of the caloric engine. The Rochester Advertiser explains the operation as follows:— The hammer in question derives its force from an exhausted cylinder—the vacuum being made by the turning of a crank by which the piston is raised and all the air forced out, when the connection is broken and the piston falls with the greatest velocity and force.— The entire weight of the hammer, cylinder, piston, and all the model in question, is but little over four pounds ; yet it is competent to give a blow equal to seventy pounds. By means of a valve and key at the bottom ot the cylinder, just so much air may be let in as may be desired, so that a light blow or a heavy one is produced at will. An eight inch cylinder will prodece a force equal to the falling of 50T pounds upon the anvil, and the repetition of the blows will be in proportion to the velocity with which the crank is turned.—Exchange. [The man who wrote the above certainly knows little about atmospheric pressure or the caloric engine. It is said that the action is like the action of the caloric engine, and that it is operated by a vacuum. Now there isvacuum chamber or cylinder about the caloric engine, and there is never a vacuum in it. The piston mentioned above never can fall with the greatest velocity and force. Its pressure never can be more than 15 lbs. on the square inch, and its velocity is measured by the well known law of falling bodies. The vacuum is lormed, it state , by turning a crank; very well, some person or machine must turn this crank. To do so a steam engine is the best power, therefore, the steam hammer is better than the atmospheric one. A hammer, however, can be operated by a water wheel compressing or exhausting air by well known means, such, perhaps, is the mode by which the above hammer is intended to be operated.