MECHANICS AND USEFUL ARTS. 21 



fire, which caused the air-pump to work immediately, and continued so 

 for hours, the fire being replenished by stopping off the blast from the 

 furnace, and opening the upper bonnet. After the air had passed 

 through the fire, the gaseous products of combustion, generally at a 

 temperature of 600 Fahrenheit, passed laterally through a chamber, 

 used for separating them from any ashes or cinders, into the working 

 cylinder before alluded to. The difficulty attending this description or 

 engine was the liability of the working parts to be deranged by the 

 great sensible heat destroying the valves, pistons, and cylinders, and 

 carbonizing the lubricating oil. 



DOUBLE PISTON "ENGINE. 



MR. TT. VIRDIX, of Maryland, has recently devised some improvements 

 in the steam engine, which relate to the employment within the same 

 cylinder of two pistons, entirely independent of each other, and whose 

 piston rods pass through opposite ends of the cylinder. One piston rod 

 connects, directly through a connecting rod, to a crank on the main 

 shaft, and the other piston rod is furnished with a cross head, which is 

 connected, by two long connecting rods, to two cranks on the main 

 shaft, whose position on the shaft is diametrically opposite to that of 

 the first-named crank. The cylinder is furnished with steam and ex- 

 haust ports at each end and the middle, and steam is admitted alter- 

 nately between the two pistons and the cylinder ends, and both pistons 

 through their connecting rods act simultaneously on the cranks and 

 revolve the main shaft. Scientific American. 



IMPROVEMENTS IN THE STEAM ENGINE. 



Two new improvements in the steam engine were exhibited for the 

 first time at the Fair of the American Institute, N. Y., in October. 

 The first was a pair of oscillating engines, coupled at right angles to 

 one shaft, the invention of Messrs. Morris and Wylie, of New York. 

 These oscillating engines have no valve rods, the steam box is station- 

 ary, and the cylinder, as it vibrates, cuts off and exhausts itself, thus 

 performing the office of a slide valve ; another arrangement about 

 it is a plan, by a common slide valve, to exhaust the steam into the ex- 

 haust passages, and vice versa, and to set on and stop the engine, thus 

 making it the best adapted oscillating engine for steamboats yet in- 

 vented. The second improvement was a rotary engine, invented by 

 Mr. Barrows, of New York. This engine is built to work the steam ex- 

 pansively, by fixed head plates, having eccentric grooves in their inside 

 faces, which guide friction rollers on the end of the blade or piston bars, 

 so as to depress them in slots, and guide the pistons out and in, to allow 

 the steam to expand in four separate chambers on the periphery of an 

 inside revolving drum. This engine has been in successful operation 

 during the past season, in a small steamboat, and is decidedly one of 

 the most perfect and effective rotary engines ever constructed. Scien- 

 tific American. 



