ADVANTAGES AND DISADVANTAGES OF AIRSHIPS The chief advantages of aircraft that are lighter than air over those that are heavier than air in warfare are:-- 1. Their speed can be variable. 2. They can hover over a particular point. 3. They can be noiseless by cutting off motive power and drifting for a while with the wind. 4. They can from their possible size have long range of action. 5. They can carry considerable weights. 6. They are endowed with sustaining power and stability. 1. _Their speed can be variable._ This advantage becomes apparent in cases where they are used both for scouting and offensive purposes. In a later chapter it will be pointed out that though the aëroplane scout has often to make dashes over the enemy, and it would be thought that from his swift movements his impressions might be vague, still, in practice, most satisfactory work has been undoubtedly accomplished. Many, however, will maintain that there are circumstances when it may be advisable for observers to proceed at variable speeds. When at a safe height it may be an advantage for the observers to take their time and leisurely survey the country, observe, and take photographs. The airship can stealthily travel over camp and fortress and steal secret after secret of the enemy. 2. _They can hover over a particular point._ The fact that the maintenance of the airship in the air does not depend upon a certain speed being maintained, as is the case with the heavier-than-air machine, endows it with the property of being able to hover in fairly calm weather. The hovering power is certainly an advantage for such offensive operations as dropping bombs. 3. _They can be noiseless._ At night it may often be possible to approach over a fortress, camp or city quite noiselessly at a low altitude by shutting off the motive power and navigating by means of the natural forces alone. 4. _They can from their possible size have long range of action._ From their size and the amount of fuel they can carry it is possible for them to travel for long distances. This quality renders them specially fitted for naval purposes, though possibly in the not very distant future more highly developed hydroplanes will run them very close. 5. _They can carry considerable weights._ The weights large airships can carry is an advantage in offensive operations. It enables larger stores of bombs to be carried than is at present possible with aëroplanes. Then several persons can be carried long distances in the larger airships. 6. _They are endowed with sustaining power and stability._ As the envelopes of airships are filled with a gas which lifts and sustains, the great disadvantage of instability which is the bugbear of aëroplanists is absent. If engines break down or stop, it does not necessarily mean that the airship must immediately descend. It can often remain in the air while the machinery is being repaired.