Waves--The subject of ocean waves fully treated--An interesting _resume_ of our present knowledge of this phenomenon of fluids. 9906 VIII. NAVAL ENGINEERING--The New Spanish Armored Cruiser Reina Regente.--Illustration and full description of this recent addition to the Spanish navy.--1 illustration. 9895 The Spanish Torpedo Boat Azor--Illustration and note of speed, etc., of this new vessel--1 illustration. 9895 IX. OPHTHALMOLOGY--The Bull Optometer--An apparatus for testing the eyesight.--The invention of Dr George J. Bull.--3 illustrations. 9908 X. SANITATION AND HYGIENE--The Sanitation of Towns--By J. GORDON, C.E.--A presidential address before the Leicester meeting of the Society of Municipal and Sanitary Engineers and Surveyors of England. 9909 XI. TECHNOLOGY--A New Monster Revolving Black Ash Furnace and the Work Done with It--By WATSON SMITH--The great furnace of the Widnes Alkali Company described, with results and features of its working--4 illustrations. 9900 Apparatus Used for Making Alcohol for Hospital Use during the Civil War between the States--By CHARLES K. GALLAGHER--A curiosity of war times described and illustrated.--1 illustration. 9900 Confederate Apparatus for Manufacturing Saltpeter for Ammunition --By CHARLES K. GALLAGHER--Primitive process for extracting saltpeter from earth and other material--1 illustration. 9900 Electrolysis and Refining of Sugar--A method of bleaching sugar said to be due to ozone produced by electric currents acting on the solution--1 illustration. 9903 Improvements in the Manufacture of Portland Cement--By FREDERICK RANSOME, A.I.C.E.--An important paper recently read before the British Association, giving the last and most advanced methods of manufacture. 9901 Roburite, the New Explosive--Practical tests of this substance, with special application to coal mining. 9897 The Mechanical Reeling of Silk.--An advanced method of treating silk cocoons, designed to dispense with the old hand winding of the raw silk.--3 illustrations. 9898 * * * * * THE SPANISH TORPEDO BOAT AZOR. [Illustration: THE SPANISH TORPEDO BOAT AZOR.]