Page:Dictionary of aviation.djvu/150

 126 DICTIONARY OF AVIATION

liomoptera ho'mepta-ea n. pi. a suberder of hemiptera com- prizing insects of various kinds, with wings of homogene- ous or uniferm texture : contrasted with heteroptera.

hood hod n.

1. a false cirrus cloud enveloping a mountain^tep or the summit of a cumulus?dome, formd by the upward air^cur- rents.

2. a covering fastend to the valwring of a balloon and extending over the gasbag which it protects from the heat of the sun, etc.

booklet 'hok;L9t n. one of the minute hooks or hook^like processes similar to the (plain) barbicels or cilia, forming a fringe or frayd edge to a barbule of a bird's f ether; a hamulus.

hoop houp, hop n. the circular band or ring of metal or other stiff material from which the car of a balloon hangs and to which are fastend the guy^ropes or cords connected with the network enveloping the gasbag above; the concen- tjating^hoop; the ring.

hop hep v. fly along or over the ground in a manner similar to that of a person or a bird that heps or leaps.

horizon ha'zai-zari n.

1. the line at which the earth and sky appear to meet; the boundary^line of that part of the earth's surface which is visible from a given point of view, or any particular part of this line as contrasted with another part of it; more strictly, the circle bounding that part of the earth's surface which would be visible if no irregularities or obstructions were present : also cald the apparent, fysical, natural, sensi- ble, or znsible horizon : as, sweeping round the *horizon ; clouds moving from one *horizon to the other.

artificial horizon, a level reflecting^surface, usually of mercury, used in taking altitudes.

axis of the horizon, an axis or straight line which is perpendicular to the plane of the horizon at the pojnt where the observer stands.

contracted horizon, an horizon whose limits are con- tracted, or whiCh is less distant or extensiv than usual en account of mist, smoke, rain, snow, etc.

false horizon, same meaning as artificial horizon.

mean horizon, the average horizon or horizon?line; the middle or intermediate position in any irregularity of the line of the horizon.

2. (in astronomy) a great circle of the celestial sfere the plane of which passes thru the center of the earth and is parallel to the plane of the sensible horizon of a given.

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