Ferry-boats of other types exist by the score, from barges upwards, propelled by an extraordinary assortment of contrivances, some of the older and quainter of which have been referred to in an earlier portion of this book. The historic Tyne ferries were withdrawn not long since for financial reasons, but an attempt is being made to restart them. The ferries at Glasgow and over the Mersey have each their own special features, and even the Thames has not always been without penny steamers. The Thames Steamboat Company and other organisations have made the experiment. The later effort of the London County Council to establish a service deserved a better fate, for the boats were well built and the engines were compact and powerful for their size. The necessity of keeping open waterways which Nature wishes to close annually by freezing over, led to the invention of a species of vessel planned with that object. The most famous ice-breaker is the _Ermack_, launched in 1899 by Messrs. Armstrong, Whitworth and Co. for the Russian Government, for which she was designed by Vice-Admiral Makaroff. Many of the harbours of northern Europe are frozen over for the greater part, and sometimes the whole, of the winter, to such an extent that the ice attains a thickness of several feet; and navigation is at a standstill so far as those ports are concerned. The only way of keeping a channel open is to prevent the ice from freezing too thickly to permit of the passage of vessels, and this is done by keeping a vessel moving frequently up and down the channel to break the ice before it can freeze so thickly as to become impassable.