There are two types of rudders fitted to steamships. These consist of the ordinary kind when the rudder is hung at its forward edge, and the balanced type which has part of its area forward of its axis. An example of the former will be found in the case of the White Star _Laurentic_, while the _Mauretania_ and _Lusitania_ each has a balanced rudder. Since it is necessary to the rudder that to obtain steerage effect there must be the motion of the ship through the water, or a flow of water past the rudder, so that an excess of pressure may be obtained on one side of the latter, it is possible for the steamship to possess steerage way actually before she has obtained motion; for the propeller race brings this about in an effective manner. The advent of the twin-screw system was responsible for a material increase in the turning possibilities of the ship, an advantage which was much appreciated when already the steamship had attained such enormous dimensions in regard to length. Thus, for example, supposing a twin-screw steamship wishes to turn quickly to port, she can do this by starboarding her helm, putting her port engines astern, and her starboard engines ahead. The advantage of the balanced type of rudder just mentioned is that it is easier to put over than the ordinary type, but it demands that the deadwood of the stern should be considerably cut away. It is only comparatively recently that the full importance which it deserves has been granted to the naval architectural experimental tank, but these interesting objects are now becoming more numerous, and yielding most valuable data on which to work. Fifty years ago naval architecture in Great Britain was certainly not on a scientific basis, and it was to France that we had to look for the leadership in these matters. But ever since the founding of the Institution of Naval Architects, and such men as Scott Russell, Sir Edward Reed and others led the way, scientific shipbuilding began to advance in this country. The results are evident in the shipbuilding history of our Royal Navy, as well as in the excellence of our splendid merchant fleets. In elucidating the many problems connected with ship architecture the experimental tank is now taking even a more prominent place than hitherto, and the recent opening of the National Experimental Tank at Bushey, where research will be carried on continuously without interference from commercial considerations, is deserving of the warmest congratulations. One of the most important tanks in the world is that owned by Messrs. John Brown and Co., Ltd., at their Clydebank works. Indeed, it may be said that no feature of this important yard is more deserving of interest. The tank is 400 feet long and 20 feet wide, with a depth of 8 to 9 feet. At the end of the tank, where the models are worked, are dry and wet docks for trimming these little ships, which are sometimes as large as 20 feet long. The latter are