“We certainly possess these vessels capable of navigating under water, which is no small advantage, but in order that they may be able to fight under these conditions and become really effective fighting machines the question of vision will have to be perfectly solved. The _Moniteur de la Marine_ affirms that the periscope, the apparatus intended to secure this power of vision, perfectly fulfils its object. It gives, six metres under water, a good enough view of what is going on upon the surface to enable a boat to steer towards the enemy’s vessel without the necessity of rising to the surface to make observations which quick-firing guns would render dangerous. No less an assertion than this is necessary to shake certain doubts on this point which will be shared by all who have been in a position to observe the troubles caused to the vision by the water and vapour on ground glasses. Only those who have used this instrument have the right to say with Polycente, ‘Je vois, je sais, je crois, je suis illuminé.’ “We who have not seen cannot go so far as this. It is also necessary that the images given by the periscope should be susceptible of rapid measurement, sufficiently accurate for the officer in command to be able to know if he is near enough for his torpedo to prove effective. “In a word, the _Sous-Marin_ and the _Submersible_ are at present marvels of applied mechanics. They will be fighting machines only when the problems of vision and accurate measurement of distances are fully solved. If this result is reached we shall not long be kept in the dark, for with modern parliamentary methods all over the world we shall witness the simultaneous appearance in all naval budgets of demands for considerable sums in order to construct these vessels.” A device for submarine vision, termed the cleptoscope, and invented by Messrs. Russo and Laurenti, is reported to be used on the Italian submarine _Delfino_. In its original form the instrument, according to the _Lega Navale_, gave an exact view in a closed chamber of all that was to be seen round about a submarine to any one applying his eye to a small eyepiece. In its later form it gives the same image much enlarged, and visible to both eyes at once at some distance from the chamber. As an illustration of the disadvantages arising from the fact that the submarine is blind, the following story may be told, the accuracy of which cannot however be vouched for. An Italian submarine went out on one occasion for practice. All at once the crew found that they could neither go ahead nor astern, nor could they rise to the surface. They pumped out the spare water that was provided to give additional buoyancy, but with no effect. The heavy lead keel provided for an emergency was at last detached; still the boat refused to rise, and the crew gave themselves up for lost.