AN INVESTIGATION OF AN APPROACH TO THE PROBLEM OF DETERMINING THE OPTIMUM DESIGN OF SHROUDED PROPELLERS. APPENDIX I. VORTEX SYSTEM. APPENDIX II. CALCULATION OF THRUST AND POWER. APPENDIX III. DETERMINATION OF THE OPTIMUM LOADING FOR A HEAVILY LOADED PROPELLER HAVING AN INFINITE NUMBER OF BLADES. APPENDIX IV. OUTLINE OF DESIGN PROCEDURES FOR SHROUDED PROPELLERS