The machine was put through the cloud blanket much as a horse takes a hurdle; it seemed unlike fog and more of a palpable substance. As we emerged, the sun was shining on it like a silvery sea with gently undulating surfaces and it looked for all the world as supportable as layers of cotton-wool. Many times have cloud-banks from mountain tops been observed, yet the upper side of the velo cloud from a flying-machine looked very different. The cloud was only four or five hundred feet thick and extended inland a few miles in irregular outline. The seaward edges of the velo cloud were not ragged, and apparently paralleled the coast for 10 or 15 miles. Such was the exhilaration and confidence the air gave that I can understand how parachute jumpers confidently step off into space, for to them the air is a supporting medium no more terrible than a transparent sea to a good swimmer. I believe that the record parachute drop was made in 1916 by Colonel Maitland, of the English Royal Flying Corps, who descended in a parachute 10,000 feet from an airplane. Fifteen minutes was occupied in the descent. _Ease of Vision at 3,500 Feet Altitude._--At this altitude the ease of vision is most remarkable. At this height, _with perpendicular vision_, the eye is possessed of wonderful powers. In those “solitudes august with stars” men not only “mount up with wings as eagles” but are given the eagle’s unobstructed vision. Birds have been credited with much too keen vision. From this height of several thousand feet every object stood out with remarkable distinctness. Automobiles racing along the El Cajon boulevard to Lakeside were readily picked up with the unaided eye although 20 miles away. Looking down over the aviation field the long compass mark and the wind-direction pennant (Figs. 19 and 20) were easily distinguished. The bay and ocean, however, gave the most remarkable revelation, for the bottom of the bay and the shallow ocean shore were plainly discernible. The absence of water as well as air refraction explains why submarines cannot hide from an airplane: one of the army aviators told me that a submarine cannot ordinarily sink so low that it cannot be seen from an airplane. _Color of Landing-ground Important._--Owing to the absorption and reflection of sunlight, there is a distinct variation in the character of otherwise similar landing-ground. A field, dark from recent plowing (or burning), will heat the air over it faster than will a field of stubble, hence over the former field there will be the greater air disturbance, and this will affect the ease of landing. Air is heated by contact and convection. One of the aviators said that recently he was descending, and had all but reached the ground when a localized convectional current hurled his machine upward some distance but immediately afterward deposited him on the ground without damage.