PAGE I. AERONAUTICS.--War Balloons.--The establishment of balloon corps in the armies of different countries; the French, English, Italian, and Russian establishments.--1 illustration 9288 II. ASTRONOMY.--Astronomical Telescopes; their object glasses and reflectors.--By G.D. HISCOX.--The dialyte telescope; practical details of the mechanical operations of construction, such as lens grinding and shaping; washing flour of emery, tests for correction.--23 illustrations 9296 Fleurials' Gyroscope Collimator.--An ingenious application of the gyroscope to fixing the horizon line in sextant observations; an instrument crowned by the French Academy.--2 illustrations 9291 III. BIOLOGY.--An Epidemic of _Micrococcus prodigiosus_.--By M. GRIMBERT.--Interesting case of bacterial poisoning, with details of the detection of the bacteria 9301 The Morphological Conditions of Heredity.--An exposition of Professor A. Weissman's theory of the "perpetuity of germ plasma;" a theory opposed to the doctrine of evolution 9295 The Third Eye of Reptiles.--The last conclusions on the pineal gland in reptiles; curious development in anatomy, the possible organ of a sixth sense.--1 illustration 9300 IV. CHEMISTRY.--Nitrogenous Principles of Vegetable Mould.--Note of the conclusions of MM. Berthelot and Andre 9302 The Lactocrite.--A new method of ascertaining the amount of fat in milk.--By H. Faber.--An apparatus for analyzing milk employing centrifugal force.--Results obtained.--1 illustration 9292 V. ELECTRICITY.--Electric Welding.--The new art in metallurgy described by Prof. ELIHU THOMSON; full details of the process, apparatus, and current required.--2 illustrations 9293 The Electric Waltzers.--An ingenious electric toy.--1 illustration 9293 VI. ENGINEERING.--Sustaining Walls. Arched sustaining walls and arched buttresses; elaborate study of French practice.--11 illustrations 9288 VII. METEOROLOGY.--Popular Errors in Meteorology. Popular fallacies; the habits of animals, the Rocky Mountain locust; the equinoctial storm 9299 VIII. MISCELLANEOUS.--Beethoven's Portrait. An authentic portrait of the great musician.--1 illustration 9301 Dwarfs and Giants.--Relative sizes of men; the Austrian giant, Francis Winckelmeler, 8½ feet high.--1 illustration 9302