This is a use which has not been much taken into account until the present war. It appears, however, one that is destined to become very general in war. It has been already used either to excite terror or encouragement amongst the population of a city either already besieged or threatened with speedy investment. It has been stated that when Liége was besieged the French aviators distributed circulars over the city to the effect that the citizens should keep up their courage, as help would soon be forthcoming. When the Germans were approaching Paris the German aviators distributed pamphlets urging the surrender of the Parisian capital. Reports also came to hand that French aviators flew over Alsace and Lorraine with pamphlets to describe the violation by Germany of the neutrality of Belgium and Luxemburg! 6. _Photography._ The value of aëroplanes for this work in war is self-evident, and various means for securing good photographs from flying machines have been devised. Some years ago the public was made familiar with photographs at great altitudes in the air by the beautiful specimens taken by the late Rev. J. Bacon and the late Mr. Percival Spencer from the cars of their balloons. Since then Mr. G. Brewer has become an adept in the art of aërial photography. The clearness of detail in these photographs gives sufficient evidence as to the value of aërial photography in war. Satisfactory photographs from balloons have been taken from as great a height as 10,000 feet. The success of aërial photography, however, depends upon the amount of haze upon the earth, which veils the plate from the actinic power of the reflected light. In taking aërial photographs from aëroplanes, owing to meteorological conditions it may often be necessary in war to take the photographs from lower and more perilous positions. The value of the photographs will, however, often be worth the risk, as very complete aërial surveys of war regions can be made from a series of photographs. For taking photographs from aëroplanes special and in some cases automatic cameras have been designed. The Germans use a camera fitted with a special Telephoto lens. In an apparatus of British make, designed by Mr. Baker, the camera is suspended beneath the aëroplane. The airman presses one button to make an exposure, another when he wishes to change the plate. 7. _Locating submarines, mines, etc._ In the present war ample evidence has been given of the deadly work that submarines, torpedoes, and mines can perform. Some years ago the late Rev. J. Bacon carried out experiments from balloons to show that when the surface of the sea is viewed from an altitude the observer has a vision which penetrates to some depth below the surface. At the time the great advantage of such surveys in naval war-time was pointed out.