The best way to regulate the flow of gas— and thereby economize It-—to the burners, is not by the burner valves, but the main valve near the meter. When the gas jets are burning, this valve should be turned to regulate the flame to the proper length, with the burner valves freely open. The object of this is to reduce the total pressure in the pipe before the gas comes to the burners, so that some gas may not escape unconsumed, as is usually the ^case when the burner valve is used as the i regulator. Root's Rotary Engine Great as is the value and utility of the reciprocating steam engine, there are even now many applications for which the form of engine called the rotary is better adapted ; in. deed, many sanguine persons believe that at some future time, which by the bye is very I indefinite, the reciprocating steam engine will be entirely replaced by the rotary. There are, however, certain intrinsic advantages possessed by the rotary engine, such as lightness, cheapness, or rather the smaller cost of construction, and from its fewer parts a consequent reduction in the friction, together with all the superiority of using directly the force of the steam. The saving in fuel which is so loudly proclaimed by many, has not, we think, been fully made out, but that the rotary engine is destined to occupy a high place among the prime movers we have no doubt. The subject of our engravings contains the above advantages in a marked degree, and from our description they will become apparent. Fig. 1 is a perspective view of the engine; Fig. 2 a vertical section, and Fig. 3 a detached section. The same letters refer to the same parts in each. The steam is admitted into the valve chamber,/, through the steam pipe, H, and passes from thence through the opening, p, into the cylinder, and presses against the piston, P, ! and also against the top of the abutment, A. The force of this admitted steam, forces the piston round, and so turns the shaft, K, the piston being keyed fast upon the shaft. The end of the abutment inside of the cylinder is fitted within a "gib" or "shoe," ^, with a knuckle or hinge joint, so that it may conform to the position of the piston, and always have a good bearing upon it. The abutment. A, oscillates on its axis, and it is worked by means of the craiik, c, connection, R, and lever, L. The shaft, K, extends out through the head of the cylinder, and on the end of it the crank, c, is keyed, with the wrist or crank pin set exactly on a line with the center of the piston. The abutment shaft, also extends through the same head of the cylinder, and on the end of it is keyed the lever, L, with the pin in the top of the lever set on a line with or opposite to the hinge of the " gib" in the end of the abutment. The connection, R, is of the same length as the distance from the center of the piston to the center of the gib ' hinge, and as that distance always remains the same whatever the position of the piston, it will be seen that the motion of the abutment will be governed by the piston, and the shoe or gib on the end of the abutment made to follow exactly the circle of the piston. The exhaust is through the opening under the abutment in the directiou of the arrow ; it passes the upright part of the abutment, (which is narrower than the chamber allowing room on each side for the steam to pass,) and passes off through the pipe, w. V is the cut-off valve which is operated by the crank or lever, n, o, and the eccentric, that can be set on the shaft, so as to cut off at any point of the stroke. The engine can be used with or without this valve. & are packing rings which are let into each end of the piston, and are held against the cylinder heads by springs under them, and they prevent steam passing between the piston and the heads, and they also protect the journal. Fig. 3 ; h being the shell, e the plumber block, and m a screw for tightning the journal; ^ is a packing plate let into the metal of the cylinder, and packs the top of the abutment across from one head to the other. S S is a packing shoe let into the piston, and kept tight against the inner circumference of the cylinder by means of springs pressing it out. E is the fly wheel, C is the cylinder, D the journal box of the abutment, and F the band wheel for conveying the power to any machinery to be turned. From the above description, it will be seen that this is a compact and convenient form of rotary engine, and does great credit to its inventor, John B. Root, of Battle Creek, Mich. He obtained a patent for it Dec. 29, 1857, and will be happy to furnish any further particulars that may be desired.