It was necessary, then, to give cruiser lines some power of resistance. This necessity once admitted, there seemed no point at which you could stop increasing the fighting power of your cruisers, and sooner or later, unless some means of checking the process were found, the distinction between cruisers and battleships would practically disappear. Such a means was found in what may be called the "Intermediate" ship. Frigates did indeed continue to increase in size and fighting power throughout the remainder of the sailing era, but it was not only in this manner that the power of resistance was gained. The evil results of the movement were checked by the introduction of a supporting ship, midway between frigates and true ships-of-the-line. Sometimes classed as a battleship, and taking her place in the line, the 50-gun ship came to be essentially a type for stiffening cruiser squadrons. They most commonly appear as the flagships of cruiser commodores, or stationed in terminal waters or at focal points where sporadic raids were likely to fall and be most destructive. The strategical effect of the presence of such a vessel in a cruiser line was to give the whole line in some degree the strength of the intermediate ship; for any hostile cruiser endeavouring to disturb the line was liable to have to deal with the supporting ship, while if a frigate and a 50-gun ship got together they were a match even for a small ship-of-the-line. In sailing days, of course, this power of the supporting ship was weak owing to the imperfection of the means of distant communication between ships at sea and the non-existence of such means beyond extreme range of vision. But as wireless telegraphy develops it is not unreasonable to expect that the strategic value of the supporting or intermediate ship will be found greater than it ever was in sailing days, and that for dealing with sporadic disturbance the tendency will be for a cruiser line to approximate more and more in power of resistance to that of its strongest unit. For fleet service a cruiser's power of resistance was hardly less valuable; for though we speak of fleet cruisers as the eyes of the fleet, their purpose is almost equally to blindfold the enemy. Their duty is not only to disclose the movements of the enemy, but also to act as a screen to conceal our own. The point was specially well marked in the blockades, where the old 50-gun ships are almost always found with the inshore cruiser squadron, preventing that squadron being forced by inquisitive frigates. Important as this power of resistance in the screen was in the old days, it is tenfold more important now, and the consequent difficulty of keeping cruisers distinct from battleships is greater than ever. The reason for this is best considered under the third and most serious cause of complexity.