These levers turn upon the pin of the propelling cranks dand e, and are guided in their motions by the radius rods h and i, connected to their upper ends. The radius rods are connected to a cast iron frame, k, which is supported on two brackets, ll, attached to the side of the vessel. The principal dimensions of the apparatus are as follows:-

Subsequently to the instance of the Maria, numerous vessels have been fitted with auxiliary steam power; and "auxiliary steamers " are now employed on several trading lines. These being built expressly for the purpose, have, in most cases, screw propellers. Amongst the largest of these vessels is the Antelope, of 600 tons, and the Emerald, of 700 tons, and 50 horse power, trading between London and Belfast; and the Sarah Sands, of 1000 tons, trading between Liverpool and Rio Janeiro.

The government likewise appear to appreciate the advantages which may accrue to the navy from the application of steam as an auxiliary. In addition to several guardships at the different ports so equipped, the Amphion, 36 gun frigate, of about 1500 tons burthen, has been fitted with a screw propeller, driven by engines of 300 horse power. By means of this steam power, she can, it is stated, command a speed, under ordinary circumstances, of nearly 7 knots per hour under steam alone; and with steam and sail combined, a speed which in all cases shall render her superior to every other mere sailing ship she may meet with. Another "auxiliary" frigate, the Arrogant, of 1850 tons and 360 horse power, with a screw propeller, is building.

The following Table contains some of the dimensions of the hull and machinery of some of the largest steam vessels yet built.